The Steve and Bucky friendship is fine, actually tbh I prefer the MCU version over the comics because I think the foundation is more solid(ymmv on that though, this is just me), and Steve's relationships with Sam and Natasha also work partly because his movies give those friendships more time and because the base-line interactions are overall friendlier(at least to me).

Steve+Clint, Tony and Thor are just... a lot emptier to me, and yeah part of it is definitely because I read the comics first and thus had relationships to compare them to, but even then to me it just doesn't feel as though the movies try as hard with those?

Unlike with Clint+Nat where the Avengers movies are always very good at showing how close they are and how much they mean to one another and despite my disinterest in Clint overall I really like that relationship because it's clear they've been friends for a long while.

Idk, it obviously works for enough people and that's fine, but for me the core-Avengers team friendships are lacking but I can ignore it to enjoy the rest of the movies. And tbh there are really solid friendships in the MCU so it's not like those not working for me is insurmountable. I just ignore the movies trying to tell me that Steve+Tony were 'super-close!!' when nothing ever really suggested that.