They aren't patching CPUs that were released 5 years ago.
They should be patching back to Ryzen 1 since those are still perfectly good CPUs. 5-7 years really isn't that old considering how little improvement there is with each generation.
Sure, not much per gen, but if you compare say a 1700x vs the current 9700x, you are roughly looking at a 3x improvement in single and multicore performance increase.
Most of desktop users don't care at all about these gains. Slap in normal ram and an SSD and a 1000 series Ryzen is ready to be a run of the mill desktop, that browses and can show media no problem.
My threadripper 1950x is from 2017… and is the cpu powering my primary hypervisor perfectly fine. That’s not 18 years ago, that’s not even 8 years ago.