It is estimated that between 30% and 50% of Internet users run ad blockers. I haven't see a single ad in years.
Besides, Pi-holes are kind of overrated. First, ad blockers running in the browser are simply more effective. Second, Pi-hole is kind of heavy for what it does; you can accomplish the same by loading a blacklist directly to the config file of Unbound/Bind/Dnsmasq.
I'm curious when I see quotes like this - are people exposing their home network to the internet? Or running a pi-hole in the cloud? VPN'ing into the home network? Or what?
I have run a pi-hole in the traditional sense (a raspberry pi with pi-hole software on my home network with my home router DNS pointing at it). But this doesn't prevent me from seeing ads when I'm out and about on 5G or public wifi or work wifi or whatever.
As an aside I stopped running pi-holes at home for reliability reasons. Lots of failed SD cards, locked up raspberry pis etc became more aggravation than it was worth. It's a neat system - when it's working.