There's an opt-in "tracking protection" checkbox in Firefox you can click that doesn't load them at all.

Hmm doesn’t it send a do not track cookie, tracker JS is still loaded and discretionary

No, it's basically a content blocker like Adblock or noscript.

I'm convinced it's not. noscript is blocking scripts and xss and does all kinds of things, while mozilla intently removed the option to disable scripts in firefox.

I do not know about adblock as I stopped using it a long time ago and now use ublock origin a general purpose blocker, but I certainly remember how mozilla was vocal about never adding a blocker in firefox as this would be contrary to <insert BS PR> (actually their business model).

Well, yeah, "Tracking Protection", as it's called, is far from what NoScript does (which does a boatload more than just blocking JavaScript). But it is quite a lot like AdBlock Plus or uBlock Origin, except not focused on blocking ads and rather focused on blocking tracking scripts (but with how many ads contain tracking scripts, it is pretty much an ad blocker, too). If you know the extension Disconnect, Mozilla uses the blocking list from that.

Tracking Protection is default-enabled in Private Browsing, can be manually enabled in normal browsing.

The "BS PR" reason for them not necessarily wanting to block trackers/ads, is that webpage owners want to make money. If they don't have a way of making money off of Firefox, then they likely won't bother testing, fixing or even optimizing their webpage for Firefox. It would make it a lot more likely for webpages to be broken in Firefox.

Default-enabling Tracking Protection in Private Browsing already caused a huge outcry and by now there seems to have developed an entire new business around privacy-respecting porn ads, so that's always nice.

That is an available option as well. In preferences, under "Privacy & Security", set "Tracking Protection" to "Always".

You write like an old grandma