> MAME would have to adapt to use the PC's CPU as the game's CPU for games like this or
> else it's some sort of digital masochism.
not really that simple tho as while it's x86 / x64 the CPU in your PC has at the very least significantly different timing characteristics, furthermore the CPU is only a fraction of what needs emulating. If you think getting the timings right on something like the Cave SH3 based games is hard, then imagine a case where they're completely different simply based on the PC you're using or what else is running in the background.
'just use the host CPU' really doesn't fit into the MAME architecture at all, and I can't see it ever fitting, it's just too different, hence why I doubt MAME will run those modern PC based games even given 100 years.
you could say "it's MAME, they'll find a way" but there are real limits to what can be done before it isn't really emulation at all.