There are many email providers who are quite profitable by charging just that and are not afraid of Gmail's absolute dominance.

If you use one of those smaller paid email providers you can still interact with people who use Gmail. If you tried to create a small Instagram competitor it's unlikely that Facebook would ever agree to federate with you.

No, but you can federate with the millions of people already using other alternatives based on ActivityPub.

People are really underestimating the second order effects from the Twitter exodus. It's not just Twitter that has a competitor. It's just a matter of time until all the Fediverse gets enough of a critical mass and then all walled gardens will lose its appeal.

Well, and do those providers have 1.5 billion users like Gmail does?

I'm not really sure whether you made this analogy to disagree or to prove their point.

Neither. The analogy was to say that their point was irrelevant. The fact that there is a network with 1.5B users does not prevent of a smaller, pay-to-join, network.

It obviously doesn't, plenty of space for niche players.

But it does prevent them from becoming the next 2B people social network which will default to becoming to go-to social media to connect with just about anyone you meet in the world.

A $1/month app won't replace Instagram (the article is about IG dying).

My sibling comment addressed this point: my bet [0] is that the next big social media network is not going to be a monopolistic walled garden, but it will be instead made by a constellation of federated providers. My belief is not that Instagram is going to be replaced by one niche app where people pay $1/month, but it will die and be replaced by thousands of smaller players who can interoperate:

- Newspapers, TV networks and streaming services who will offer a "free" account to their Mastodon (or similar) server for paying subscribers.

- "Influencers" who will be hosting their own ActivityPub servers

- Companies who will realize that they can put all their marketing communications under their own control and branding.

- Fringe communities who will be running their servers just because they can.

- Commercial providers who will look for something that can differentiate themselves (privacy, custom clients with special features) and charge for it.

- etc, etc, etc.

[0]: By bet, I mean that literally. This has been one of my side-projects and I've put already a non-negligible amount of time and money into it. Thanks to Musk, my service has seen more activity, signups and inquiries about custom hosting in the past 3 weeks than it has seen in the first 3 years.