(Disclaimer: I work for Mozilla)
I am sorry but tracking protection on mozilla as it is now (only enabled by default on private windows, and hapening with no user knowledge/information/learning oportunities) is a lame clutch.
I wish they'd focus more on getting the UX of containers up to snuff. They are almost there, but still far enough away to make addons like Multi-Account Containers (MAC) something I cannot recommend to my parents.
Here is what I mean: Suppose I want to keep my use of example.com separate in it's own Example container. How do I do that?
1) Click the MAC icon in the toolbar, then click the "+" button.
2) Enter 'Example', pick an icon or color, then click okay.
3) Open a new Example container.
4) Navigate to example.com in the Example container
5) Click the MAC icon in the toolbar, then check "Always open in Example"
6) Close the tab.
7) Open a new tab, and browse to example.com
8) Click "Remember my decision"
9) Click "Open in Example container"
This is nuts. I can't recommend this workflow to anybody.
Outside of that I'm sure turning ad blocking on by default would break several sites.
Also publicly, they've said that ads are an integral part of the web.
What's the difference of shipping a feature off, and shipping with support for an extension (on both firefox and Google's chrome store sites!) that can be installed? At this point we are just discussing semantics. Install vs Turn on.
Note that they already included something similar, which is SafeBrowsing(TM), that is maintained by google. Technically, it is exactly the same concept. But uBlock is actively request by 99% of their users, while safeBrowser(TM) fingerprinting is mostly disabled by half.