1. Software has bugs.
2. Bugs which interface with and execute untrusted code are high risk.
3. Browsers are obscenely large pieces of software, which connect a user's system with random websites which execute JavaScript.

Browsers are one of the most important things to update on your computer.

We can talk about whether browsers should be as complicated as they are, but implying security updates are a intended as a vector of control is conspiricist thinking.

The reason you don't get security updates backported to your older release of choice is simple: it is so much work.

Waterfox seems like a good choice, just don't go around thinking that companies are making security updates in order to sneak in unwanted, they make security updates because they are terrified of being responsible for a major incident.

Firefox is open source. Outdated open source is dangerous (even more than outadred closed source IMO) because people can literally look at the code and find every single bug. Even if they use security updates to roll out features or antifeatures, there are also security patches. And once those are out, now the entire world knows about the bug (because they can see the source changes). If you stay out of date, you are exposed. That simple