Couple things. Verizon exclusives, and verizon branded phones, including the Pixel are notorious for not providing OS updates. I think in the entire time I have been using smart phones on Verizon network, first one was a Motorola Droid Maxx about a week before the Droid Maxx HD came out, I have gotten a total of 1 update per phone. This is not an issue with Android, but an issue with Verizon. I have heard that Verizon is one of the worst for that. The reason is because all OS updates have to go through the provider, and that costs money.
If you outright buy a non carrier locked phone, your updates come direct from Android. That being said, I have used Motorola Droids since I went to smartphones, and have yet to get a bad phone. My only regret is not having the cash to outright buy a phone not carrier locked.