I think some people get lost in their rotations or distracted by other stuff a lot of the time. I imagine some have level / story skipped. I know some folks have had other people play for them.

First boss takes a little time to learn if you've skipped raids and don't understand the concepts of Exaflare and the dorito mini-stack.
2nd boss is relatively easy, dancing around to avoid AOEs. The buster is something they introduced in Puppets Bunker.
3rd boss is actually the simplest. Avoid the butterflies.

This game demands you be aware of your surroundings and everything generally builds on past experiences. There's plenty to be figured out if you just stop and look at the area and what's going on.