I thought a bit more about it and I think one of the big issues is that this film has, what, 12 protagonists? Which means that it's trying to do too much. And the villain has only about 3 lines and is basically a video game big bad. The final action scene in particular has the bad monster facing off against all 12 protagonists.
Some of those characters just shouldn't be in the movie. They don't contribute anything; they just clutter it up and take screen time away from others.
Bill Murray and Annie Potts, both pretty much pointless. Do they even do anything other than just pop up and be there? Podcast and Lucky not only don't really contribute anything to the plot, it stretches credibility that they'd even be in the city at all. They feel forced in. James Acaster I'm not so sure about... I guess they needed somebody talk technobabble, but surely Stantz could have done that? Cutting those five from the script would have made for a better movie, I think. Drop Walter Peck, too. I don't think he really added anything to the movie.
And it clearly suffered from some major editing/rewriting. Ray just appearing in scenes he wasn't in (once at the big lab, once at the Firehouse), there were scenes in the trailer with them in the red jumpsuits which didn't make it into the movie, and the villain must have had more than 3 lines originally. It felt like there were missing scenes, and some jumps didn't work.