My Ad Limiter add-on is down to 19 users on Firefox. Used to be thousands.
It won't work on Chrome at all now. I'm shutting down SiteTruth, after almost 20 years.[1]
I don't remember what I've used before uBlock Origin, but since its appearance it's basically solved the ad blocking on Firefox and became the de-facto standard for the browser.
You probably lost all your users to it, rather that they all stopped using FF.
Most likely AdBlock Plus. It was basically the standard until they started allowing advertisers to pay to not have their ads blocked.