@TalismanRing
I understand, but I'm talking about when strip the plot down to the bare bones.
Falcon and WS's relationship with Steve need Steve, that is true, but they feel a bit like some side action of the main plot. Winter Soldier is basically a henchman, and Sam is a guy with no vested interest in SHIELD who joins the fight because of Steve. He doesn't have the kind of role that, say, Rhodey had in Iron Man movies.
The prime characters aside from Steve are Pierce, Fury and Natasha. None of whom are traditionally associated with Cap. In fact, Pierce, despite being the big bad is more of an adversary for Fury than for Steve.
I enjoyed Sam and Bucky's roles, but they felt ancillary, basically a hook for Cap3.
Of course, the fact that SHIELD has been infiltrated by HYDRA does necessitate Steve's involvement. Which is why it just bugs me a little, as opposed to actually ruin my enjoyment.