And that is actually confirmed by filmmakers. Evans straight out said, that Cap is selfish and chooses Bucky over his new Avenger's family. That's it.
Cap is compromised. And his being "compromised" has nothing to do with Sharon quoting Peggy about compromise in the eulogy, btw. He was, as were the rest of the Avengers, seemingly engaged in the necessary discourse to get reach consensus on the Accords and what happens? Peggy dies.
Now Steve is conceivably already stressed from his life as a super soldier in the 21st century not to mention having just gone through a pretty costly mission. Yes, he's functional, but he's also suffering some of the dysfunction that comes with stress the least of which is a certain amount of resentment and some loss of judgment especially when he has to deal with rekindled and convenient attraction to Sharon and the framing and discovered whereabouts of Bucky.
And yes, he chose Bucky over the others. Bucky has been a major focus for two years, and Bucky is in the most immediate danger of being terminated. The others are full-fledged Avengers, all of whom know the responsibilities and dangers of the job of being an Avenger. They all had freedom to choose.
But, yeah. I'd agree he's a little selfish, but how could he not be under the circumstances?
Anyway...
But if somebody wants to see Cap as white and pure as he was in the previous films, then there is no point to argue about it, because the movie provides pretty good excuses for Steve to not make him too bad. They obviously worked very hard to balance these things well.
Was he thus in the previous films? I think people who choose to believe this over simplify the character and/or have selective memory. In TFA, he was a scofflaw when it came to the service recruitment process. Attempted enlistment 5 times which was expressly against the rules. Falsifies information. Can't stay out of a fight. Etc. He also mavericks off on a mission to rescue Bucky and company on his own authority with Howard and Peggy as his willing accomplices. More on "willing accomplices" later. And he swears and makes sausage eyes at Peggy.
In TWS, he manhandles BW, is borderline insubordinate with Fury, indulges in a little self-pity with Sam and Peggy, breaks about a dozen doors, steals a car, sabotages government property with "willing accomplices", and swears. Again.

Potty mouth.
Steve IS somewhat of a boy scout, but he's not Duddely Dooright. He's not "St. Steve". Because this is not that kind of genre. He's a little more complex than that and that's good because he would be a stone cold bore otherwise.
The movies are never going to make any of the Avengers seem too bad, not intentionally. That'd be the kiss of death. (What we the fans choose to see is another thing. We like to knock our heroes off of their pedestals from time-to-time, it seems.)
Once again - yes, Steve still is a good man. He meant well. But he has found comfortable excuses for himself and was okay with it. Avengers have become criminals because of him. That's an objective result of his actions. And for what? There was no need to fly to Siberia.
Steve has a strong and define ethos and he
rationalizes his actions in accordance with that. All of the Avengers who followed him in the evil super soldier gambit also refused to sign the Accords and followed him
willingly. And they all believed there was a need to get Siberia and stop the supers. Steve being Steve could not possibly NOT pursue, because it was conceivable that Zemo could have been after that particular human capital for no good use. Again, judgment. How hard would it have been to discuss this issue with Tony as a legitimate threat? (And of course, Civil War answers with, "enough talk. UNDEROOS!") Movies. smh.
The fact that the villain set it up to be a mission in vain was the point. Of course, the villain was motivated by actions directly liked, collectively speaking, to the Avengers, so there is that.
As well as there was no need for Sharon to risk her job, because if Steve is capable to break in the Raft without shield, he is totally capable to steal wings and that shield himself. All these sacrifices were all for nothing.
I stand by my thinking that Sharon risked nothing, and turned over the weaponry with full intention of informing on them for "the greater good". Not that she would be duplicitous, but that she would believe her duty would be in alignment with Steve's mission. Get Zemo, stop the world threat. No one in authority is listening to Steve at the moment, so either he would stop Zemo, or the authorities would stop him and follow up on the threat after they had Rogers in custody.
Yes, Steve meant well, I stress about it, yes, maybe in the end Tony has made much more mistakes but Steve was wrong too.
Why stress about any of this? They'll all be pardoned by the time Infinity War rolls around. Actually, I wouldn't be surprised if we find out the Accords have been repealled or redacted or what-have-you by the time Tony Stark shows up to hog the spotlight in Spider-Man.
Now, having said all this, I don't know how much longer the Avengers can operate without some sort of structure around them. Privatization with Tony footing all the bills didn't work, S.H.I.E.L.D. and the WSC didn't work, UN/Accords was suspect. Infinity Wars might be the last hurrah.
On another note, I'd like to speculate on how Steve accomplished the RAFT jail break. Who wants to bet that we find out that Fury/Hill/Widow were the principals involved?