What to do when your supervisor is not really supervising you?
Given the constraints and assuming that you can't move to another institution, I think you are stuck with coming up with your own plan. A well known and respected advisor is an advantage to you provided that he signs your thesis and writes a good letter of recommendation, even if he doesn't do anything else. Sad? Yes. Probably true. 

My suggestion, in your huge lab, is to try to start up a study group in which a group of three-six students decides to meet regularly and discuss their work and any blocks they have. Study groups are a feature of Law School, of course, and some other disciplines. Perhaps you can adapt the idea to your work. It would depend on how closely your work aligns. If too different, it probably wouldn't work. 

I will also note that some professors consider letting students work almost entirely independently as a feature, not a bug. This is probably more common at the doctoral level, but the large lab you are in makes it almost mandatory. But the ability to work as an independent researcher is an important skill for any academic, though being forced to do it too early is a disservice. 

The best advice, however, is to get the thesis done, get it signed, and move on. Look for a better situation in the future.