Hardening Firefox – a checklist for improved browser privacy

Shouldn’t Firefox come hardened out of the box ?

Yes, but a lot of Mozilla's money comes from Google. https://www.pcworld.com/article/2772034/googles-search-monop...

There’s tradeoffs between privacy and convenience. Mozilla makes a particular set of tradeoffs, based on their judgment of what the average user will put up with; checklists like this allow you to make more aggressive tradeoffs.

That would be a great move by Mozilla. Have a "secure" version: Firefox, Firefox ESR, and Firefox SECURE. Or maybe just provide a switch to turn on.

Isn't that just to provide the search engine default? Which is easily changed?

90% of the stuff in the OP will break certain sites… The problem is that non-technical users will think “oh, privacy, that’s good” (which it is, don’t get me wrong), click the “max privacy” option, but then be unable to fix things when they don’t work and switch back to Chrome.