I think Spectre may have appeared later, after Meltdown? Remember the investigations into what's possible were proceeding in parallel with the attempted fixes.
Also, CPU design changes take a long time. 6 months may seem a long time from the perspective of HackerNews node.js type hackers, but it's a bit harder to patch decades worth of CPU microcode than a website.
I get it may take a long time (that is fine even if the patches took a few more days), what I don't get is that they released it to production (server) envs seemingly without testing. Surely even rudimentary testing (deploying on a few 1000 different server platforms for a few hours at least should be something that Intel does for all microcode updates, after all they are rather more important than js Node packages as you point out)
I haven't heard of microcode updates that hurt stability before. Presumably the collapse of the embargo caused them to do an accelerated release, skipping their usual long testing cycle.
Currently, they are not patching a decade worth of CPU microcodes since we have 0 working microcode. And, previously, released microcodes were only down to Ivy Bridge EP (~2014).
Also, CPU design changes take a long time. 6 months may seem a long time from the perspective of HackerNews node.js type hackers, but it's a bit harder to patch decades worth of CPU microcode than a website.