Either Google, and other advertisers, put me in the "uses adblockers, be aggressive with ads" pool, or they've moved on to using DoH/DoT/etc in general. I've been able to confirm this by observing Google and other Android apps making TLS connections to known DoH/DoT/etc IPs, and blocking them worked.

At that point, you need more complex routing than what a simple DNS blocklist can provide via Pihole, and if you want good throughput, you're going to want real networking hardware and not a RPi.