Literally all the Jedi we see doing the same job as Anakin in the Clone Wars are masters. He's given a high-level command and put in charge of some of the most important campaigns of the war working as an equal in rank to sitting members of the council.
I'm not even saying he should be promoted, every reason they give for not wanting to is justified, but the Jedi put a lot of responsibility on his shoulders because he was very good at his job and then denied him the rank and titles associated with those responsibilities, of course he sees that as a snub.
A bit of both, I think. Mace kind of draws the short straw of the main prequel Jedi of being the one who wasn't in the original trilogy and is thus the least important that the audience likes, so he gets the worst showing. He still gets cool moments, but he also ends up being the one who represents the worst of the Order.
See, I think being given the fancy new desk but not the faceplate is the actual snub. Not getting promoted because your elders think you aren't ready for the responsibility is one thing, getting a de facto promotion out of necessity but with your boss making it clear that you haven't really been promoted is a clear insult.