Some of us tried that, right after Google's Motorola acquisition. Didn't work out so well for us. (It was the only "Google" option at the time for those of us who needed to be on Verizon for their network specifics.)
Right now, I'm on a Nexus 5x that works on Verizon while not officially supported. Verizon network, without the Verizon crapware and retarded (as in, delayed or never delivered) security updates. I might move to the Pixel 2, when it comes out. Even then, I'll buy it directly from Google and forego the Verizon crapware-and-delay leash.
Samsung seems to have a renewed commitment to timely updates, and the moxie to pressure U.S. carriers to pass them on -- somewhat.
Other than that, I'd advise most of my friends to stay away from Android on U.S. carriers. It continues to be a shitstorm. My friends with Apple remain mostly simply happy and unstressed. I'm not particularly fond of "walled gardens." But for a lot of people, it's "just a phone" and they want it to "just work."
My point regarding Google itself: They bought Motorola and had Motorola thence promising timely updates for a reasonable period of time. Didn't happen.
I trust Google to do what it perceives to be in its best interest. Including updating its own phones for PR reasons. Beyond that, just like the newer products they launch or buy and then often kill a year later, it's a crapshoot.
P.S. Like others are expressing, Google's a big place with many pieces. As to the topic of the OP, I'm glad Project Zero continues to have support and is doing what it's doing. And that it has the muscle and inertia of Google behind it, to weather the political and legal shitstorm attendant with the mess that is is IS/IT security, these days.