Its quality necessarily subjective here? sometimes seeing is believing. The final Endgame battle scene was not as sharp in the eyes. The blur color dilution of the movie, the cinematography could have been a lot more polished. The movie is very animated than real life. See it here for yourself.
Even Weblurker, the biggest mcu fan I know had to agree that the CGI scenes of Nighcralwer in X2 looked more life action and less animated than Endgame . At least Avatar had one hell of amazing CGI scenes that was beyond beautiful to behold and groundbreaking that I never knew could be created in a film. The Avatar story may have been crap but the movie made up for it technically. I don't think this is subjective, I think it is objective as we can compare both movies on paper to see which one did better in various different categories.