Imo builtin AdBlockers is much worse than addons. You have no free choice, have to trust that the devs will provide updates regularly and accurately (in contrast to just switching to another AdBlocker when eg. uBlock breaks), and are fucked once they decide it's too much work/Google pays them a nice sum to not block them/they decide to just replace the ads instead of removing them.
Addons on iOS, just as on Android, are very much needed and an actual solution to a whole plethora of problems, that no browser on its own could ever solve.
Maybe the problem is not Firefox here, but Apple.Apple does not allow other browsers than Safari on iOS. All other browsers are just reskins of Safari.
You know that feeling when you just knew something for years and it feels so fucking funny and awesome to actually see that reflected in studies? Yeah.
You're an idiot for trusting anyone. Especially entities whose only purpose is to generate revenue and serve fascists.