Re: Any kind of central "real world identity" system is RIPE for abuse. Period.
"What's the incentive for big ISPs to maintain a complex decentralized infrastructure when their users are happy enough with their simple central silos? There is none."
The answer is dead easy. Existence. As in existential class actions against such ISPs (in a broad sense), which are not only foreseeable but foreseen by certain devs (that also happen to be trial lawyers) quietly building the technical infrastructure to create and support properly pleaded "lawyer-less decentralized class actions".
If you want to predict the future, it's hard. Until and unless you actively create that future. You don't even need funding or community "support" until you choose to deploy, that just slows everything down. It's so easy to do that Zuck did it with his dystopian present, so why not anyone?