That's like saying when you grow your own tomatoes you're dependent on the weather or your capability to deal with said weather. That is true. But it misses the point. When you grow your own tomatoes and the store sells only a certain bad tasting kind, suddenly wants to increase the price by factor 10 or stops selling tomatoes at all, then the value of growing it yourself shows. And they are dependent on the weather just like you.

If you self host, you're dependent on things sure. But the point isn't to reach some hypothetical perfect state of independence, the point is to get the flavour you want, not have to deal with them changing their business model, and so on.

The reason I self host my webservers is because my webhoster decided to charge a premium for SSL certs. So much in fact that for the cost of one cert per month I could run a webserver for a year.

Then I had my mailservers noster taking decisions I didn't like, so again I went and self hosted.

Some of those things are running for a decade now and I have yet to experience the catastrophic events you mention. Sure you need to do your due diligence and know your craft, but at least I am ot affected by someone changing their business model or deciding it isn't profitable anymore.