If that was true, then why don't we have a fork of Firefox being developed by the community that is better than Firefox?
The only thing we have now are forks of Firefox. Sure, some are better, but all still rely on Mozilla's upstream contributions. If Mozilla stopped supporting Firefox, these forks would be dead. They just add some features and UI changes. They are not working on web standards, fixing implementations of those standards, or security fixes.
Mozilla gets fucking loads
From Google. And if that deal disappeared, Mozilla would probably go bankrupt or rely on a worse deal from another provider. Neither would be good for Firefox development.
It makes sense that Mozilla wants to branch out, diversify. It just sucks that they're terrible at doing it. Would have been cool if Mozilla operated like Proton or any other privacy-orientated service provider.
most open source software manages to avoid ads, why do you think that is
Because they have scruples and usually have financial issues as a result.
They get some small donations from some users... and Google.
It being open source means nothing. Open source developers still need to eat. It just means that you could remove all the things you don't like.
To my understanding, you just need a phone number to make an account. I think it can be a burner number. But then if you ever lose access to the account you can't recover it.