Even the first Avengers movie was like that (an extreme amount of green screen acting, the cgi/special effects looked very cheap to me almost bordering on made for tv). Yes cgi has come a long way (cripes remember how rubbery the cgi was in the first Raimi Spider-man movie!), but its nowhere near perfect.
I only have the dvd version as a reference point (probably the problem lol). It doesn't look as flashy as it did at the cinema, I guess I better get a 100 inch screen ? . The movies length meant the dvd version was going to be a hard task to convert to something watchable (as most 3 hour movies generally push the capacity of a dual layer disc). From memory the Peter Jackson King Kong dvd version was similar.
From what I have read the blu-ray and 4k releases are not what they could be. In that they've not used the entire capacity of the discs available. The theory is that they will release a new version in the future where the picture quality is improved even more. As they hadn't done a proper 1:1 conversion from the filmed version (which was filmed on a 6k camera iirc).
I watched it on a Samsung 75 inch and thought it looked gorgeous. It may get better, but i am more than happy with it as it stands
I have no doubt they struggled to get the DVD copy onto a disc. The movie is HUGE!