And the solution involved un sanction and prison for disobeying. Cap opposed it and didn't waver. He wants a solution not that solution. Agreeing to a crappy solution isn't resolving the problem. From his PoV it wouldn't. In fact Iron Man goes seeking his own solution No u.n. So who seems right?
And these films will go on and on accordingly. Like a lot of these films the theme can developed not be resolved in one movie. It's not a reset model like Bond so it can snowball.