I mean, does that mean Edge is a Google browser, too?

Chromium is open-source. Even if Google adds something malicious to the source code (such as that Web Environment Integrity stuff), it can be removed by someone else creating their own browser based on Chromium. That's the very definition of open-source.

Related side-note: Lemmy itself is open-source, too. If the creator of Lemmy added something to the software that someone running an instance didn't agree with, they could simply fork the original software and remove the unwanted addition. Some people do disagree with that person's views, and yet they're still here. Many of them joined .world and other instances instead of .ml because they disagreed with the creator's views.

While Google, the creator of Chromium, isn't a good company for the consumer, I personally think Chromium itself isn't a bad idea. It's just that Google and some other companies modify it for their own means, and those means aren't always consumer-friendly.

All that to say: while the company that originally created Chromium is bad, the software isn't. And while some of the companies and people using that software are bad (including Brave, IMO), some of them are looking out for their users' interests, and those forks of Chromium are generally ok. (You should still actually do research and not pick a fork because the company developing it said it's okay, though. Take a look at what others are saying and verify it.)