Aren't most people using ad blockers these days, making the revenue that one can generate with ads trivial unless traffic is enormous?

You would be surprised to how little people use adblockers. Old data, but on my country for a major tech website, the number was 13%.

Popular in tech circles, but largely unused outside them.

It seems to me at its root, that it's a question of available ad attention, and the value thereof.

The classic value prop for ads has been so badly destroyed by bad curation and content invasiveness that the basis value of that attention has dropped trough the floor. The growing prevalence of ad blocking is only a symptom of that.

This has become bad enough it even invades special interest nonprofit rags like the AAA, American Legion, and USPSA newsletters, for example.

My experience deploying at blockers in the enterprise is the average non tech user feels the Internet is "broken" when it's not covered in ads and will tell helpdesk it needs to be fixed.

Unfortunately not. Adblocking is a security requirement and should be enforced by any enterprise.

I never used adblock because if I don't like ads on a particular website I will simply not visit it anymore. And if I like it enough despite of the ads, I want to support them financially in some way.

About 30% from what I could find.