This is a very long standing issue and it has been raised for years from time to time. The issue at hand is not just collision shapes.
It’s an entire real-time cloth physics engine, which is quite old and I do not really see anything which can be presently used to substitute it. For the feature of such magnitude RL usually so not spare time to develop in house and rely on third party tools/API integration (maybe AI is the answer for future integration?).
Given all that, it is still possible to have long garments to properly simulate with acceptable quality. I have given a lot of tips and examples on this and legacy forums.
On the other hand you posted in CC forum and I assume this is where you are looking to simulate garments. So check THIS post where I demonstrated a clip and explained (in a few posts above it) why Character Creator is not suited to run cloth simulation and iClone is the only way.
Also check this old post in legacy forum: Cloth streteching issue