But today everything but Firefox is Chromium.

That's a little different

And 20 years ago everything was IE (at >90% penetration)

The problem is Chromium ,not Chrome

Like you have the illusion of choice, that's what I'm talking about and that's different

Firefox entered into a contract per-install with Google that did no evil while Google iirc was building their own browser secretly.

Browser engines are now open source a lot more than they were.

I don’t think it’s about illusion of choice as much as some browsers actively working to degooglify themselves from Chromium and maintain it.

Some browsers are maintaining their own forks, others aren’t.