Ad blockers usually block such stuff, for a good reason. But I don't mind it on a checkout page specifically though, because on a checkout page I wilfully disclose a ton of my private details, such as name, address, etc.

Good checkout pages work well with an ad blocker on.

It's just the paradox of when you present yourself as "the good guys" - people will hold you extra accountable for things that others easily get away with as nobody expects them to do better.

Unfortunately, Mozilla tends to shoot themselves in their foot this way somewhat often.