Spammers destroyed an open email system that relies on a centrally controlled DNS. Probably because they were among the only ones who learned how email works. We never made the effort to teach the population at large, preferring instead to let email be centralized via "email providers". And now, after decades of spam, we still have people who argue it is the best, or even the only, way to do things.

Spammers did not destroy the protocol or well-designed email servers and clients.

"Very few people should run their own email server"

That mindset is why we have a problem, in my opinion. We have actively tried to prevent people from learning.

The history of block lists is a history of the failure of the "email provider" (i.e. "very few people should run email servers") idea. Of course, anti-spam is a career for some people, so "failure" is relative. They've succeeded in trying to exert control over a common internet capability, for profit.

The internet began as peer-to-peer. There was no "DNS". And there were no "email providers". Everyone had a responsibility to learn how to use the network and the basic services it could provide e.g. messaging. Then some people got some bright ideas about how to make money. "Spammers" were not the first ones.

Enjoy that spam in you inbox. It is the product of ignorance.