I don't know, at the end of the day I thought it was great. It would have been really gay if it had ended with some kind of Avengers like fight between good and evil.
Evil fails because... evil is bound to fail. It might take over, but eventually due to its very nature it's always gonna fuck up. It's never gone for good, but it's gonna go away for a while.
"Overconfidence is going to fuck you over" is an overarching theme throughout the whole book, it starts with the people who built the captain trip's virus facility, the people who created captain trip, the guy who thought he would be able to get away, the entire world dying because they thought they could contain it, the guy who experimented on stu and the rest of the team were also far too overconfident in their own measures and died as a result.
It just goes on and on and on. The other team is "treat people nicely, or it's going to come back and bite you in the ass". They often go hand in hand, too. Nadine, fat boy, etc... all had a chip on their shoulder, all thought they were special, all pushed people away... and all failed as a result.
People dicked over Trashcan Man because he was weird, and he ended up making them all burn.
Yeah, it's anti-climatic, sure, but some gay ass dragon ball z fighting in the middle of Vegas would have been much worse.