It could be about 1,000 different things, including hardware issues completely unrelated to the OS. I also have a PC with a 7900XTX on Linux 6.18.2, using Plasma/Wayland and I've never had an unrecoverable system crash. Two of the other people that I game with are also running the exact same setup (Arch,btw/Linux6.18.2/Plasma/Wayland) without issue.
Blaming graphics cards sometimes feels like a meme. Its like if someone has any kind of problem and happen to mention that they use NVIDIA, you'll see a huge portion of commenters, with nothing other to add, jump in to imply that it's probably the NVIDIA card.