One of the problems with the PhD system is that individuals have to carve out something that is theirs, they own it. That becomes their dissertation. It doesn't sound terrible said like that, but the most productive work I've ever done was after I graduated and got a job. A small group of people with equal ownership of a problem and solution can be so much more productive. The requirement that a student defend a body of work that is theirs disincentives them from doing, what I think, is the most productive kind of work that leads to the best research outcomes.
You can work in productive groups in grad school, but you still need to find that part of the work that you can claim ownership of. Because if you don't, you won't graduate. This means that inevitably, you're going to have to think in terms of "what do I need to do to get the hell out of here" rather than "what's the best way we can solve this problem."