You sound like you don't want anyone to be able to buy new stuff.
If all you want to do is have a stable platform for 3600-3900x (dunno about 3950x, probably wouldnt risk it) then i don't see the point, and frankly the reasons for getting a X570 are really niche.
The fact that PCIE 5, DDR5 and what not are coming soon, these boards are clearly priced with that in mind, the fact is that AMD wanted the older boards to be compatible, so the new boards have to price that availability in as well, especially on the thicc ego booster boards.