the whole "backward compatibility" softening of consensus years ago has its disadvantages
if nodes are not part of the vote nor even validating data.. then that is a bullcrap feature
the whole idea of fullnodes validating fulldata across the network is the whole point of bitcoins invention.. which has been ruined with this bypass trojan generator in 2017
That's nonsense. Full nodes have never been part of the voting process from day one which never changed either. It has always been 1 CPU 1 Vote (aka miner with actual hashrate) not 1 Node 1 Vote. The reason is pretty simple, there is no way to know for sure the IP you connect to is actually running a full node or is faking it or is one of many IP addresses linked to a single node (in other words you can run a single node but with many IP addresses pretending to be that many).
You also seem to be ignoring the history. The first soft fork (with backward compatibility) if memory serves was BIP16 (ie. P2SH) which happened over a decade ago in early days of Bitcoin.