Having lurked around gcc for close to 5 years, it seems to me like whole patch review culture simply stems from the fact that there is not a single person who cares about the compiler as a whole. Sure individuals care about their passes (IRA stands out here as being well taken care of), but seldom as to what happens outside of it. And when people do do reviews it very much feels like the response is just "I'll just ack it to get you off my back" which obviously doesn't do wonders for quality. Unless a Linus-of-GCC person comes along, I don't see much long-term future for the project.
The recent decision to move the project code base to C++ is also something that I think will actually hurt them badly in the long run. The GCC code base is very hard to read as-is and moving it to a language that is notorious for being hard to read and understand will not make things any better. (I'm well aware that some amazing pieces of code have been written in C++, but it is not a simple fix to the code cleanliness problem)