I think they meant, can't a visitor just ignore that your cert is self-signed and view the page anyway, _without_ adding it to the trust store. Firefox, at least, has this as the default "ignore the cert error" action.
That said, "can't a visitor just ignore that your cert is self-signed and view the page anyway,"
No. They cannot. Not when it's HTTP/3. Even if the browser ostensibly supports it the HTTP/3 connection will fail because the HTTP/3 lib Firefox uses does not allow it.
That's the point the other poster is making, it adds a new level of control that becomes the de facto only way to do things if http 1.1 ever gets deprecated.
I have no opinion on the likelihood of any such deprecation but I fully understand the concern.