It's almost every day I encounter a website that I choose not to use or choose to use in a degraded form because the intended experience would require me to install or configure my user agent in a way I do not desire.
Is it? 42% of internet users used ad blockers last year. That's an upwards trend and is surely going to be much higher on a niche browser compared to browsers that are installed by default. Firefox does not come with an ad blocker by default.