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.
On my phone I do both: I use AdGuard DNS to block ads system-wide, and Vivaldi's built-in ad blocker to block those ads that still slip through.