That's actually a good point about how some services do require payment to provide safe service to their users. A very close to home example would be your local Lemmy instance. In order to run the servers and keep it ad (and tracking) free, each instance needs donations from their users. The same is true for Mastodon, as you mentioned.
The problem is, I would be shocked if Twitter actually provided a safer (or improved in any way) service. There are a other issues at play as well, but they all basically boil down to most users not wanting too give money to Twitter, and if they were ok with that, they would already have purchased Twitter Blue.