Unpopular opinion, but I use Firefox because I care about privacy and the spirit of the Mozilla manifesto, and this new enabled-by-default advertisement feature snuck into the browser is at odds with both.

Mozilla never even gave their users a warning in their browser, which is even worse than how Chrome handles it (also enabled by default, but they at least included a notification with a corpo-speak justification that includes similar language about "options" and "privacy".