I think some of the issues people still have with Assassins Creed Unity parkour are completely solvable.
Lots of the time I see people complain about how despite the fluid cool animations in unity, the longstanding bugs mess with the control you have over Arno. Now I'm not saying this is wrong at all, its entirely true, sometimes Arno just seems to not be entirely aligned with what your controller is directing him to do. But I think people saying this hurts the parkour is a bit extreme, its definitely not ideal and I completely understand the argument that it isn't the best parkour in the series, however the problems aren't unsolvable pains. All of the jank and annoying movements are more results of inputs, I find the game works best when you kind of just go with the flow, some people dislike that but hey that's how it works.
But one thing I will admit is that I may not have the full picture, I was still a kid in 2014 and my parents were telling me to play minecraft instead of games about being a sneaky murderer. So that meant I didn't deal with any of the release bugs, I only played the game years after it released when I could get it on my own accord, and by then most the glitches had been patched. So all I really got was the cool, well animated, smooth parkour and not the abysmal game that dropped back in 2014.
I also wanna clarify that I'm not trying to argue Unity as the best parkour game in the series, I do think it is but there's no actual reason to care if other people think otherwise, we all have opinions. I'm finally playing the original AC at the moment and I really enjoy the puppeteer control over Altair and how he performs parkour and I definitely see how people prefer this type of parkour.
I really just think people overblow the issues with Unity's parkour, it's a lot of fun if you just stop fighting against it.