u/kazinator is decidedly wrong (see above), but besides not trying CJK unification, I wish we had had UTF-8 from day 0, no UCS-2, no UTF-16, no BMP, no codespace limit as low as 21 bits. That's mostly it. If we could have stood not having precompositions, I'd rather not have had those either, but that would have required a rather large leap in functionality in input modes in the late 80s or early 90s, which would not have been feasible.
kazinator is wrong, decidedly so, but let me take this opportunity to opine my own impractical list of gripes that require going back in history and redesigning Unicode in fundamental ways ...
That 'list of gripes' is all about the single change of having UTF-8 from the start. It's not multiple separate problems.
Also why are you implying that any gripes automatically prove you right? It's kind of ridiculous to suggest that not having UTF-8 was people "deciding to make it complicated to bolster their egos".
What we are contesting is your characterisation that the people in charge of Unicode added complexity in order to puff up there egos. Rather then them making decisions that with the benefit of our present knowledge was the incorrect ones.