Except, of course, that there are IRC clients accessed through browsers, mail through browsers, Usenet through browsers... so you don't actually exclude people that way.
If Gemini catches on, someone will write an add-on for Firefox that reads it. And then it's just part of the Web that is fast and looks a little different.
And that link is a long-winded way of saying "It's good to put an artificial barrier in the way."