You keep saying this but it's just NOT TRUE.
This is why there is a 1MB base blocksize limit.
The old keys can spam away at their 1MB block all they want. The new keys which are 'disarmed' from quadratics can spam away at the 4MB total.
You cannot attack this way, no matter the sigop count, we could remove that limit. Sigop limit's are only a bandaid.
You simply cannot craft a tx that takes 10 minutes to validate with only a 1MB block. And segwit isn't quadratically spammy, so 4MB is OK.
It's precisely why segwit+2MB HF was the dumbest proposal in the world. That would be quadratically attackable.
1mb, 4mb is just data limit..
if there was only the 1mb limit. then quadratics could make a single tx of hundred thousand sigops taking HOURS to validate..
this is why there is the maxtxsigop limit.. to reduce quadratic risks.
in recent years it got added and put down to 4k sigop limit and 20k blocksigop limit. meaning quadratic spammers can no longer make a single tx of hundred thousand sigops. but at most 5x of 4000 sigops.. which calculates to 50seconds of validation time instead of hours
your also forgetting that native keys will still be functional even after segwit activation. so the attack still exists.
all sgwit key users are doing is disarming themselves from performing it. but people sticking with native keys can still perform it.
and as my other post mentions.. which most people dont realise is that segwit keys need to be in the base block too.. even if their ass is hanging out in their weight area.
its not like segwit key users are completely separated from native keys, just their ass (the sig/witness)