Then you’re just going to be at the mercy of the people that do run these things

I wasn’t asking for a way around them, I’m asking why they exist and suggesting we collectively move on from them.

I realize maybe my response was taken as disagreement

You may not have intended it but your response was a dismissal of my concern. Rather than discussing why it’s necessary or whether it should be removed, you suggest that I create my own alternative.

As a product owner I’d want a way to contact

You can. We’ve already been over this. Send them a message on the platform.

or validate a user

How is an email address validation? I can spin one up in 3 seconds.

Self service password reset

You’re just creating a security vulnerability.

I’m not trying to defend email, just curious what mechanism could take its place.

Again, I already explained this.

Some platforms only require a username and a passkey (not even a password). That is ideal, in my opinion.

Email is also used to track user activity across the web, and while you know whether or not you will be tracking, collecting, and selling my activity, I don’t. Removing email eliminates that concern.

Some sort of cryptographic signature might work

That’s called a Passkey.

though I would have to think carefully about no separate communication/ confirmation channel

Again I ask, why? What is this fixation on multiple communication methods? Maybe as the user I don’t want you to have other ways of contacting me?

If you really need it there are hundreds of alternatives.