TL;DR: Smite rework for clarity, wtf scuttle crab why are you making a speed shrine, small camp buff rework/redistribution for clarity, Baron visuals for clarity, inhibitors really suck at clarity.
TL;DR included because oh god, this is way longer than I thought it would be. It's pretty easy to navigate; if you're not interested in a certain thing, skip to another thing with the bolded headings. With that of the way, let's get into exactly what I feel could be done to improve the unclear systems:
Smite: With Smite's new functionality, I feel it should be reworked completely to: "Spirit Hunter: marks a target monster; when it drops below a certain amount of Health (390-1000), Spirit Hunter executes them, stealing a large amount of Health (and mana?) from the target. If that creature has a non-Epic buff, also steal that."
If cast on a monster marked by an enemy jungler's Spirit Hunter, the amounts of execute damage are added; if the total would kill it, the buff goes to the most-recently cast. If not, when the execute triggers, it goes to the team that most-recently dealt damage.
As a supplementary system, implement the following FREE Trinket: "Spirit Stone: Has Jungler passive. Stores up to one effect from the most recent non-epic monster slain with Spirit Hunter (summoner spell). When used on an ally (including yourself), bestows the stored buff onto them. If you already have a stored buff when you kill a monster with Spirit Hunter, its effects are immediately applied. Spirit Stone can be upgraded into one of several forms after killing a certain amount of monster camps with Spirit Hunter (not level dependent), upgrading your Soul Hunter ability:
1: Soul Harvester: Marks all non-Champions in an area near your target with Soul Hunter. While marked, damage dealt to them is amplified and restores your health and mana. [For farming; weak to buff steals since, ideally, this will be applied early for the sustain.]
2: Soul Reaver: Marks all non-Champions in an area near your target with Spirit Hunter, amplifying damage dealt to them. Non-epic monsters executed with Spirit Hunter grant 50% more gold, but take 50% longer to respawn. [For counterjungling.]
3: Soul Burner: Spirit Hunter gains charges for each monster camp killed. Spirit Hunter can be cast on any enemy, including Champions, granting vision of them, slowing them, and consuming the charges to deal True Damage over time based on the charges consumed. Casting Spirit Hunter on an enemy Champion marks them for execution, at 10% of the execute value for monsters (39-100). [For killing stuff in ganks.]
4: Soul Crusher: Spirit Hunter can be cast on enemy Champions. When cast on an enemy Champion, they are marked for execution at 10% of the execute value for monsters (39-100). For the duration of the mark, you are granted vision of your target, and their damage 'to you' is reduced while your damage 'to them' is increased. [For dueling in or against invades.]"
Issues this fixes: (1) Clearly communicates that you are taking something from the monster. "Why should a giant orange sky-laser grant you a monsters' buff?" is a harder question to answer than "How did I get this buff while stealing things from that monster?" (2) Bridges the divide between tanky and spanky junglers. The set health sustain (stealing from camps) means more effective health on junglers with more defensive stats, while the fighers' higher damage output means taking less damage, anyway. (3) QoL: prevents accidental buff steals by or from your own team; if the jungler wants it, they get it, and if they don't, they just transfer it over with Spirit Stone. (4) Against low-health (execute range) monsters, it retains its instant damage, as previous; stealing buffs and objectives in their last moments is still equally effective. (5) Junglers' "jungling item" doesn't interfere with their core build in any way, shape, or form. (6) Zero worry about laners abusing the item; Spirit Hunter (summoner spell replacing Smite) is necessary to make use of the trinket.
Since we're talking about monster camps and their buffs, let's talk about camps and their thematic relationship with their effects:
Scuttle Crab: Easily the worst offender. Why does an odd little crab-animal create a vision/speed shrine? Change it to a River Demon. In its normal form, it lurks beneath the surface of the river, taking reduced damage. While CCd, it floats on the surface, and takes amounts of damage that make killing it a realistic venture; it should take teamwork (to mimic its current behavior). Killing the River Demon with Soul Hunter grants "Blessing of the River Spirit: For so long as you hold this buff, the River Spirit will aid you" to any allies that assisted in the kill. When the demon is defeated, a thankful River Spirit spawns; as long as any ally with the Blessing is nearby (being in the adjacent lane is close enough), she grants allies near her a movement speed boost, health and mana regeneration, and vision of the area; she also slows enemies passing through the area by the same amount. Why does she only work when an ally that helped her is in the area? This makes it such that the objective can be lost if laners die and the jungler gets dead or absent; counterplay prevails!
Wolves: Essentially, switch with Bird Bros. Wolves are stealthy, sneaky hunters; make this buff the hunting/invading tool. Wolves grant "Blessing of the Hunter: You gain a small amount of movement speed when near an enemy Champion. When you would come within sight range of an enemy ward or trap, it is revealed and disabled instead. After standing still for a short duration, the location of enemy Champions within vision radius is revealed, even through Fog of War".
Stone Bros: These tanky, rocky mofos don't scream "execute damage" to me. Instead, "Blessing of the Rock: you gain resistances and damage reduction". As these are currently the first camp taken, this buff continues to provide the stats needed to make it through the first clear, except in the form of resilience instead of damage.
Bird Bros: Birds seem much more predisposed to the whole "scouting" thing than... spiritual... wolves (that only spawn sometimes; where is the clarity?!), so let's switch that: "Blessing of the Observer: You gain a small amount of movement speed while out of combat. After standing still for a short time, summon a spectral Razorbeak, which will grant true sight of a small area for a duration, or until an enemy champion enters the area, at which point it will grant true sight of that Champion for a short duration before expiring."
Gromp: As the hard-hitting beastie he is, his poison can be made offensive, rather than defensive, filling Stone Bros' previous niche as the bonus-damage-camp. His attacks inflict a bonus magic damage and a poison DoT, and killing him with Spirit Hunter grants "Blessing of the Toxic: Enemies you attack and enemies that attack you take magic damage over time."
Unfortunately, the issue isn't limited to small camps:
Baron: While, previously, Baron was a Champion-centered buff and so was adequately visualized by the buff on the Champion, that is no longer the case. Baron's primary influence is on modified minions, and its visuals should reflect that.
When Baron is available, the area of the river around Baron Pit could gain, with highest intensity at Baron, himself. It should be instantly clear that Baron is a source of some huge, influential power.
When slain, Baron's power should visibly transfer to (1) the players of the killing party, in the form of a visible aura; (2) the nexus of that team, which should make it clear that the minions that it is spawning are receiving a benefit from the buff; and (3) the empowered minions, themselves.
While near a Champion with the Baron Buff, the Baron-influenced minions will display a more-intense visual, indicating that they're under the influence of the Baron-Buffed Champion.
Overall, exactly what Baron makes stronger and when it does so should be significantly more obvious.
Blue Buff: Blue Buff is a giant stone monster that hurts a lot when it punches you, which does absolutely nothing to communicate that its primary purpose is to augment spellcasting. I propose the following: Blue Camp's primary damage comes from visibly charged-up, high-impact lasers from the small monsters; the large monster either doesn't attack or has massively-reduced damage. While the large monster is alive, it funnels energy into the small monsters, charging their high-impact laser significantly more faster and so allowing it to fire more frequently (making up the difference in damage); when Big Blue dies, their rate of fire slows (such that they deal the same damage that they do, now).
This interaction indicates that "the blue buff makes magic better" much better than "big rock monster with big punches", but the overall camp damage remains unchanged.
Red Buff: Red Buff can be as simple as the large monster's damage being redistributed between its base attack damage (reduced) and an application of its own effect to its target, damaging and slowing it. Total damage can easily remain the same.
For that matter, clarity isn't limited to monsters, even:
Inhibitors: The fact that destroying an objective on the other side of the map makes stronger minions come out of your Nexus is huge lack of clarity, in my humble opinion. One possibility would be to spawn minions at the Inhibitor; destroying it stops minions from spawning, which has a similar impact (the lane pushes). Alternatively, a buff could transfer from the downed inhibitor to its counterpart, granting it the ability to spawn super minions, bolstering the waves from the Nexus.
Regardless of execution, there should be some local visual that clearly describes the interaction between killing an Inhibitor and the friendly lane's increase in power.