Mostly agree with you.

For me the best approach for defense is both limiting space for spam + spam filters together with the financial incentives. As you say Bitcoin is Monetary network, not a multiple purpose decentralized database / shitcoin.

The more friction for spammers, the better.

And I would like to point to the fact that all shitcoins are worthless centralized grabage scam created out of thin air but due the strong propaganda ordinary people are getting brainwashed and are throwing their money into the casino shitcons. So we can not fully rely on incentives.