Bad:
they killed off Taskmaster immediately (probably to prevent the "New Avengers" being made up of 50% Russians)
the Russian accents were bad, I don't get why Hollywood insists on doing this shit when they could just hire people who are actually from those countries
the second half was bad, it felt like two separate movies stuffed together
they kept side-lining Bucky, instead they shoved Yelena into the spotlight but he was so much more compelling than her still
there was no real build-up or chemistry between Bob and the mercenaries, so it made no sense when they all hugged him to defeat the Void (seriously)
using the Watchtower again was just nostalgia baiting and it failed
the sudden jump from Bob not knowing how to use his abilities to instantly knowing all of them was ridiculous
Sentry's design was awful, and his power-set was so misplaced for a film about super-soldiers, it was like when they put Adam Warlock in GotG3 and he was massively underpowered and misplaced
they really needed to focus more on the Void being "empowered" by shame and misery, and so would feed on the Thunderbolts to get stronger, forcing them all to face their own pasts and come to terms with it (Bucky should be the first to overcome the Void, as he has progressed the most in that already, then he helps the others)
the ending made no sense, they had the villain cornered in front of cameras and STILL let her lie her way out of it, they could've just detained her publicly after she tried to claim credit, and then told the world she caused the problems and they had to fix it
the end credit was a massive spoiler and made it pointless to watch the new Fantastic Four trash
That's probably me done now for Marvel. I don't see it going in any direction where it will be interesting any more.