Reddit, Facebook, Amazon, Youtube and Googles search ads aren't affected by the built-in tracking protection at all.

That alone are half the pages most non-tech people (like my parents) usually browse.

I remember seeing a list of domains which Firefox tracking protection explicitly whitelists (presumably to avoid breaking these sites’ functionality). Google and Facebook were in there. That told me all I needed to know about this supposed tracking “protection”.

Really? Are you sure you don't have some other hosts/vpn based ad blocker? I surely don't use Firefox Preview for much, but I definitely saw an ad on Preview when I was using it yesterday. I forgot why I wasn't using it -- aside from the fact that Firefox normal is in the quick access icons -- and since my phone had just restarted I thought I'd give it a go. But I quickly saw an ad and thought "oh right" and went back to normal Firefox.

> Regardless, Firefox Preview already blocks ads and trackers perfectly fine the built-in tracking protection.

I don't want a blacklist of ads and trackers. I want all third party scripts and frames blocked by default, which uBlock Origin does perfectly.