Out of curiosity, could a version of capitalism with limits potentially prevent exploitation?

It really depends on how you define terms. "Exploitation" as communists use it is not a moral hazard as much as it is the name of a relationship between two components in a system. Step out of economics and morality and look at an ecosystem. The reason any given species thrives in an ecosystem is because it occupies a "niche". That niche is predicated on exploitation of specific source of energy (or whatever needs the organism has) which is exists in sufficient abundance as a result of some other ecological component. Bees do not make flowers, but they require flowers for their energy source. The flowers produce that energy in abundance, so the niche that bees occupy entails exploitation of the excess energy from flowers in order for bees to exist. If flowers did not produce available energy, or if they suddenly stopped, the niche would essentially close and the bees would cease to exist.

When we bring it back to economics, exploitation is a the mechanism by which a "species" (i.e. a specialization of a broader category e.g. bees are a speciation of animals or life) maintains its existence. In the Marxian analysis, human society specialized into classes and the mechanism by which the owning class maintains its existence is by exploitation of the abundance of commodities produced by the working class. If the working class did not produce a surplus, or if it suddenly stopped producing a surplus the owning class would cease to exist.

So can capitalism exist without exploitation? That depends on whether you think capitalism can exist without an owning class that does not work. Generally speaking, I don't think there's a way to frame capitalism without an owning class that does not need to work. Once you have the concept of surplus and combine it with private property, you have the ability for private persons to accumulate surplus and cease to work. If you eliminate the right to private property, I would think most theorists would agree, you no longer have capitalism.

But what if the laws were written to prevent grotesque wealth accumulation

If you mean that the state could appropriate surplus and redistribute it, you've essentially truncated the right to private property and limited it to a centrally planned definition of what "enough personal property" is. With that surplus appropriated, you then need a central planning function to determine how to redistribute it. I think you immediately leave capitalism as soon as you suggest this.

I think of communalism as being similar to communism, and multiple tribes from around the world naturally discovered it. Is communism a new phenomenon, or a return to what we had before? Maybe humanity is undoing a long-standing mistake.

Yes. 100% However, it's important to distinguish between types of continuity and types of rupture. For example, if the Europeans had genocided all of indigenous cultures in all parts of the world, and the world was 100% white people, eventually we might re-evolve darker skin around the equator, but this would not be the same as saying that we have returned to what we had before. It would be a new instance of immanent phenomenon.

Even if indigenous forms of communism existed, it would be inaccurate to say that the Russian revolution was a part of that historical process. The ideas transferred and produced a new instance of the phenomenon, but they do not share a continuity in the same way that Dutch and American capitalism share a continuity.

This distinction is hard for me to articulate well. Because if the ideas transferred, then clearly there is some sort of continuity at play here. Two armies in two totally different parts of the ancient world fighting for completely different territories are two discontiguous processes, even if they both informed their strategies by reading Sun Tzu. If those two armies formed an alliance and captured territory together, their discontiguous histories would merge at some point, and the present would be contiguous with each of their histories independently, but the histories would not become contiguous retroactively. If the armies, instead of forming alliance, entered into combat and one destroyed the other, then the history of loser would continue only in so far as the victor failed to completely terminate every subprocess of the loser's history.

It's an area I don't honestly have a full grasp on. There's a book on it I've been meaning to read, "Continuity and Rupture" by JMP, but it's on my list.