Not ideal, but (at least on desktop) you can set the Home page to a blank page, and there is an extension called 'Blank New Tab' that I've been using for quite a while.
Firefox's global traffic market share is less than double digits [0] and is less than 5%. Google technically doesn't need traffic from Firefox and Google is roughly paying half a billion ($585M) a year for it. [1]
[0] https://gs.statcounter.com/browser-market-share
[1] https://stateof.mozilla.org/pdf/Mozilla%20Fdn%202024%20-%20A...
I'm not aware of any adblockers that can block the ads on the built-in New Tab page. (You can just disable them in settings anyway.)