the movie made it pretty clear that cap was in the right
which is another slight annoyance with this film, it never really felt like anyone other than cap and iron man were at odds with each other. and it wasn't really a fight between fundamental ideologies like the comics stressed
widow and hawkeye even have awkward friendly banter while kicking each other's asses. spidey and antman are just kinda along for the ride because why not. black widow was always on cap's side and it seems like they threw her in iron man's camp to even out the numbers and to use her as a plot device.
that said I realize this is a superhero movie
I thought what Widow said in the initial argument scene made some sense - the stuff about "winning the public's trust back", and how she was trying to keep one hand on the wheel, to work with the UN rather than against them. I thought her being in agreement with the accords made sense for the pragmatic nature of her character and her switching sides to Cap - because ultimately she's more loyal to him than the accords - also made sense.
I don't completely disagree with you, I just think you're going a bit far - Ant Man and Spiderman added so much to the spectacle of that one fight scene, but their appearances are really contrived and that possibly detracts from the movie as a whole. Hawkeye was there because Team Cap needed someone to "rescue" Wanda and Wanda was only there because she was rescued. And Bucky for obvious reasons.
But I think Widow, Cap, Iron Man, Falcon, War Machine and Vision at least all laid out their positions pretty clearly. I really liked those scenes, both the one at the Avengers compound where they argue about the accords and the private one between Cap and Iron Man in the office, with the FDR pen.
you make a fair point about the supporting cast and widow in particular.
I think my lingering beef with this movie is that the scale and scope of whole thing feels really tight and limited compared not only with the original comic but even the movie Winter Soldier before it.
the source for the strife was a bombed building, not an entire elementary school. the pool of heroes actually at odds with each other is about 3v3. there was never any animosity between anyone until the very last 2v1 fight (which I admit wad amazing). the bad guy in the end is some single dude pissed about his family being caught in collateral damage.
and also the film kind of lands too neatly with "cap was right all along" rather than maintain a moral ambiguity that i feel like the whole civil war idea is supposed to maintain ---
...Snrk. And theeen, we do stuff like, 'Persona!' with our Personas and beat the crap outta Shadows...