I think there's a range of optimal techniques for any given situation. The more narrow the situation, the more narrow the range of techniques. Boxing keeps a fairly narrow situation, so there's a narrower range of techniques. Kickboxing gets a bit broader, and so do the techniques that serve there. MMA is broader yet. And we see each of those situations comes to a fairly common range of most common options, a second range of selectable options that vary among the successful folks, and a smaller range of options that seem to work for some people.Or if everyone winds up pretty much looking the same when they fight then there really is an optimal system for fighting.
Now, that doesn't meant there's one "right" style. If we consider the range of situations we could find ourselves in outside competitions ("the street"), there are a lot of styles that seem to cover parts of those (I don't think it's possible for any style to cover all of them). And because what we could expect is less predictable (wider range of situations), there's a wide range of suitable systems (and some that appear to be unsuitable).
And some systems cross over reasonably well. With sufficient skill, there are a lot of systems - even specialized ones - that become reasonably suitable for the street. Some (like boxing) fit reasonably well at moderate skill for a lot of the situations the street could present, and are problematic with others, even at higher skill levels (MMA showed this with the ground game).