The current “directory tile” ad experiment shows only for new Firefox users. A new “enhanced tile” program to launch soon will mean existing users can see some ads, too.
Well, this is exactly why I stopped using firefox. I do not want ads in my browser, also they endorsed DRM in HTML5, contributing to a further lockdown of the internet in the name of copyright.
They had their chance of being relevant, but we have better alternatives now. Use a firefox fork such as Pale Moon or Waterfox instead, don’t support what Mozilla has become. And especially don’t switch to Chrome, either.