Most people who run servers aren't cloud hosts, so they're not running untrusted code on their servers in the first place, making Spectre/Meltdown pretty much a non-issue.

These sorts of issues were discovered a decade ago when speculative execution first hit the scene, we just never had a practical exploit (in public knowledge anyway) until recently, and even then it really isn't that bad despite all the security apocalypticists shouting that the end was nigh.