I think the problem here is that we're expecting a film to equally focus on everyone, which, a) the first Avengers didn't actually, it focused on Tony and Steve and Bruce and Natasha, and Loki, to an extent. CW focused on Steve and Bucky and Tony with strong secondary Natasha and T'Challa and Wanda, and I'm actually impressed that it managed to include all those storylines as competently as it did- the Russo's movies in this franchise have been a lot more even-handed and streamlined than Whedon's more explosive and character-focused, IMO.

b) This was /meant/ to be a partisan movie, focused on Cap and characters relevant to his theme and focus, which, in this case, was the freedom/accountability dichotomy, with Steve cast as the purist and Tony (& Natasha) as the compromisers. Wanda's and Bucky's storylines were examples.

Personally, I really liked that it had so many characters, even with uneven screentime (personally I'm like where the fuck was Hope Van Dyne), because that's more true to life than would be a story where everyone had an equal hand in driving along the plot. You ever been in a big friend group where all the drama is always focused on two or three people? Yeah. Tony and Steve are those guys.