I think where I would disagree is in wording.
I think a human fighter allows nearly unlimited creativity, but doing so requires a player with imagination, and DM that's open to them doing it. Truth is, a lot of players don't want creative characters that make them really open up. They want at least some degree of comfort in their character. Tropes exist for a reason, in other words.
But, yeah, in any system I've ever seen, a standard human fighter tends to be the best blank slate for going all out with.