Just look at the most recent changes to webextensions that chrome is trying to do... basically solely to make ad blocking nigh impossible. That's why browser diversity matters.

Is that different with Firefox? I haven't been paying attention in a while now but I constantly read complaints about UI changes - and Firefox has it's share of experimental features that ended up being exploited or abuse (asm.js comes to mind).

It's not much different with Firefox, no. I was making a point that browser monopolies are bad; the fact we only have three real browser engines (two of which are based on Konqueror) is a problem.

But at least Mozilla do a basic back-of-the-envelope “is this feature a huge security vulnerability” check before shipping. (Looking at you, <portal>.)

Only in the sense that when Google wants a new web standard the Firefox devs need to be convinced before it happens there. That has stopped a few, but not all, user hostile things from becoming defacto standards over the years.

When Google invents a feature I want, Mozilla writes a position statement on how it's evil and never implements it.

It's hard to get behind engine diversity when Mozilla is trying to take the web in a direction I don't really want.

Meanwhile Brave does the same thing, but with Cryptocurrency.

I wish we had an open source clone of Vivaldi.

What features are you referring to?

FLoC may be one that could be characterized as “evil.” I mainly think about APIs that extend beyond the browser, like USB or Bluetooth, that Firefox won’t do for security reasons.

Those are the features I was thinking of.

FLoC seems to be pretty irrelevant to anyone not directly working on ad infrastructure, so I'm fine with Mozilla ditching that.