The good thing about new AM4 boards being available at this point in time is you have options to keep older hardware running. Usually the CPU and memory will out-survive motherboard. Much like those new Chinese motherboards supporting 4th and 6th gen Intel CPUs, this is great for longevity and reduces how much production is needed

In a sane world, the limitations of a CPU socket would be reached, and then newer SKUs would no longer be released

I'd argue that it would be best if computers were more like cars, a new platform gets released each decade or so, and small improvements are made to individual parts but the parts are largely interchangable within the platform and produced for a decade or two before production is retired. More interchangable parts, slower release cycle and more opportunities for repair instead of replacement