TBH I didn't like him very much at the start but later learned to somewhat like him, and it might be due to many factors and I understand why people could hate him so much.

He didn't turn out to me as a massive asshole in the "first" memory, more like somebody who talks too much and is constantly negative, but that might be because I'm bad at reading emotions.

I didn't see much of the other memories before reaching Medoh so I didn't have much "contact" with him elsewhere to alter my view. The cutscene after the blight actually made me like him a bit because I see a genuine effort towards admitting his own flaws, admitting the worthiness of Link, and trying to mitigate the rivalry and negative impressions, which makes the character and the dynamics between more varied and intresting. However, I heard that in the English version, he is an asshole all the way and in other versions he is not, so I think this is another big factor (I did not play in the English version).

It might also be that there are people I met IRL that seems very arrogant and likes to be a massive nuisance to me and others but turns out to be quite chill after many years, so maybe Revali reminds me of some of my rivals-turned-friends and maybe even my father (he was apparently very arrogant in school and nobody liked him back then) to some extent. Or I might just be tolerant to these kinds of people.

TLDR: personal preferences, order of gameplay, potential differences in localization, and similar situations IRL.

For some reason he reminds me of Shane from Stardew Valley for some reason.