The big difference between email spam and blockchain spam is that the former has virtually no cost, and the latter extracts a cost that miners are happy to pocket. They have to pay to put their Angry Ape crap on the blockchain. And the larger the inscription, the more bytes it takes up, the more expensive it is for them. There is a negligible cost for node runners in hard drive space. I run a node, and this does not bother me at all.

I say, let them pay. This fad will eventually whither away and tx fees will continue to decline. The solution is worse than the problem. Spending precious dev resources figuring out ways to filter this spam is not a good use of their time and furthermore, it will create new problems. The spammers will always find a way forward. E.g. They will pay miners directly to validate their bloated transactions. The side effect will be that miners who welcome this extra revenue will become more profitable than others and over time, this will centralize mining even more than it is today. This is a much worse problem than a bit of blockchain bloat.

Ordinals do not pose an existential threat to Bitcoin. It is a mere annoyance to some, and a novelty to others. The best solution, IMHO, is for Bitcoin devs to do nothing and let spammers pay for inscriptions, and allow this ridiculous fad to fade away into historical irrelevance. You want to stuff shit on the blockchain, you have to pay for it. That's the way it was designed.