> The Pixel 8 Pro has hardware WiFi problems, the 9 and 10 are both minor updates

The prime difference between P8 pro and P9 pro is that the newer one is nearly a usable size (just about fits in a pocket now). The battery also got substantially better in two ways: on mobile data (when you're on someone's WiFi, odds are you're also near a charger) you get 33% longer use time on all variants of the P9 and 55% on the P10 and P10p (9 to 12 and 14 hours, respectively), and hours of use per 30 minutes of charging went up from 4.6 for the P8 to 6.3 for the P9(p) and 6.2 or 7 for the P10 and P10p, respectively

The rest is indeed relatively minor but it's not an unwelcome upgrade. Prices didn't change much when buying second-hand 1.5 years after release, when the newest devices are out and nobody cares about the generation-before-last despite >5 years of updates remaining (plus however long you think it's fine without updates)