Brush up on your continuity bruh. Comics or movies really.
Cap is riddled with guilt for thinking he didn't save Bucky and was shellshocked when he found out he was alive. It's been an underlying obsession to find dude given he's still so stuck in the past.
Also just peep Cap's moves, decisions and reasoning. Son thought it was a smart move to not restart SHIELD. He wanted to defend the world with his little Avengers squad. This being only like a few months or year since the invasion of NYC. Son is insane on the low. All that's happened is more threats have popped up. Threats even he isn't aware of (see AoS for everything Coulson has handled without Cap having a clue). Dude thinking it's still the 40s when it comes to the big picture. You let Cap be in charge of the heroes and the villains will always have a place to thrive.
Cap's problems and approach to crime fighting is well documented. Dude needs therapy, don't front.