AI might help fix disease but if it really can make progress towards disease, it certainly won't stop there and it will help us extend lifespans too, and everyone being super-healthy for hundreds of years can't be a good thing for overpopulation.
I think you can easily just say "here's problem XYZ, let's use AI". Well, that's a rather lazy argument because it's hard to envision how AI will help and moreover, I think the onus should be on the inventors of AI to really demonstrate that it does anything useful at all, because it's not at all clear how it can help anyone.