The main advantage of ARM right now is that there are low power cores available. The actual instruction set is unrelated to this advantage. If Intel or AMD put more serious effort into power efficiency most of the advantages go out the window.
As for instruction set changes impacting what software you can run I think that is still a big issue. Yes porting to ARM is straitforward in more modern programming environments but most software actively developed at the moment has a lot of old cruft that won't easily port if the engineers can even be convinced to touch it. Most businesses are dependent on old software not all of which is still maintained. Most gamers are even more tied to old software that is not going to get ported and often has annoying anti-virtualization checks (see games breaking on systems with enabled intel e-cores).
I am not sure how large the modern non gaming personal pc market is (tablets, phones, works computers, and chromebooks probably took a chunk out of it) but that could be in play.