This is also my experience. But to be fair I have a heavily modified privacy-centric Firefox, and I disabled some features in the config, and I disable js and large images and of course tracking/ads by default, and I delete most cookies on browser close, and I run Wayland on Linux so... any breakage is probably on me.
I almost always find that when sites do not work with Firefox (also Wayland on Linux) it works with Firefox (on the same machine) without the same plugins and settings.
Enabling JS is not enough, so I think its liked to privacy plugins, or running inside a container.
the cynic would say if you can't be tracked, you can't be monetized. unfortunately, being successfully un-de-anonymizable means you can't be distinguished from a bot.
