Good morning !
I am also a bearer of bad news, as I am also encoutering CTD since I've installed GSX.
To be frank and honest, I might had 2 to 3 CTDs maximum since I've bought MSFS2020 back in August 2020 (with two different systems).
But since yesterday, when I've installed GSX, I haven't been able to complete a single flight. CTD occured at least 4 times in the last 24 hours, and happen either during boarding, or sometimes on final.I've also had CTD 1 hour after take-off.
CTD were common for me during the P3D era, but they almost completely disappeared with MSFS for me, and last time I've got one was maybe last year (I don't remember having one those last months).
I'm trying to insist on that, as like many other users, I suspect GSX being a part of it (but not completely as you suggested).
I was really happy to have that immersive addon back with the new sim, but it's a shame that I'm not able to fully enjoy it.