I'm a bit confused? Most security issues can be solved with microcode updates, kernel-level mitigations, or compilation level mitigations? I'm not exactly sure

I'm a bit confused? Most security issues can be solved with microcode updates, kernel-level mitigations, or compilation level mitigations? I'm not exactly sure why this is as big of an issue as you make it sound? Realistically, anyone who cares about security should turn off SMT, which fixes speculative vulnerabilities (which is most of the serious ones). Additionally, a lot of the headlining vulnerabilities these days seem to require physical access of some kind, more relevant for portable devices. Edit: the best solution of course would be to have Coreboot.