I don't think the idea of GC is to save you from thinking about memory allocation. Actually, not thinking about memory allocation is a great way to create very slow programs, independant of whether you us an GC or manually free memory, though modern GCs keep the performance penalty reasonably low. Still, you want to think about memory allocation, so that you don't allocate inefficiently.

What GC delivers is first of all the guarantee of correctness, a pointer is either nil or points to a validly allocated memory. Also, it removes most needs of bookkeeping. That simplifies programs and especially allows to write clean APIs, where functions are fine to allocate reasonable amounts of memory.

But wherever there are large parts of memory required, especially with a clear lifetime, I think a lot about memory allocation and even in a GC language I try to reuse memory wherever that makes sense.

So for a game engine, there should not be much need for allocation during the run time of a "level" and thus GC pauses should only happen between levels.