It's not a conspiracy theory. Could you point to the 'debunking' because I don't see one that contains any actual evidence?. There are lots and lots of public mailing list posts by RMS and other GCC engineers explaining their reasoning for not making GCC more modular. The reasons were political.
For example RMS vetoed the first attempts to add support for Java bytecode to GCC because he thought it would allow people to interact with GCC from other non-free software: http://gcc.gnu.org/ml/gcc/2001-02/msg00895.html
That same reasoning is why there is no GCC equivalent to LLVM IR or libclang or libtooling.
https://lists.gnu.org/archive/html/emacs-devel/2012-12/msg00...
Part of the reason why clang/llvm weakens our commnity, compared with GCC, is that the clang front ends can feed their data to nonfree tools.
There are some links in this wiki page that cover some of the arguments made against adding support for plugins to GCC. http://gcc.gnu.org/wiki/GCC_Plugins under 'Potential disadvantages of supporting a plugin architecture in GCC'
Here is a post from a GCC maintainer explaining that RMS was personally blocking the inclusion of this much desired basic functionality for political reasons: http://gcc.gnu.org/ml/gcc/2007-11/msg00193.html
> Is there any progress in the gcc-plugin project ?
Non-technical holdups. RMS is worried that this will make it too easy to integrate proprietary code directly with GCC.