There's an impedance mismatch between people who think gcc should have maximized user utility vs. the actual GNU philosophy. The actions of the gcc project make a lot of sense if you consider the FSF/GNU are monomaniacal about maximizing users freedoms, and not popularity, momentum or other ego-stroking metric.
GCC today has a very interesting license term, the GCC Runtime Library Exception, that makes the use of runtime libraries like libgcc free if-and-only-if you use an entirely Free Software toolchain to compile your code with; otherwise, you're subject to the terms of the GPL on libgcc and similar. That is a sensible pragmatic term, and if they'd come up with that term many years ago, they could have shipped libgccjit and other ways to plug into GCC years ago, and the programming language renaissance that arose due to LLVM might have been built atop GCC instead.
That would have been a net win for user freedoms. Instead, because they were so afraid of someone using an intermediate representation to work around GCC's license, and didn't do anything to solve that problem, LLVM is now the primary infrastructure people build new languages around, and GCC lost a huge amount of its relevance, and people now have less software freedom as a result.
You're right:
https://gcc.gnu.org/legacy-ml/gcc/2005-11/msg00888.html
> If people are seriously in favor of LLVM being a long-term part of GCC, I personally believe that the LLVM community would agree to assign the copyright of LLVM itself to the FSF and we can work through these details.
With the benefit of hindsight, I'm glad that that didn't happen, even though I have mixed feelings about LLVM being permissively licensed.