I had the 3a for three years, passed it on to my son who used it three more years. Bought a 6 after the 3a, used it for three years and passed it on to my son. I am typing this on my 9a. Never had any issues on any of those phones. Either I have been very lucky or you got two rotten apples.

The 8 had known screen issues, and they were fixed even out of warranty. After six months it would have been within warranty, so you definitely should have been able to get that fixed. I know, I had to have mine replaced too.

I've had a 4, 6, and 8. No issues. But I know that if I do have hardware issues, Google will address them like these screen and battery issues.

Before the pixel existed I owned a Google Nexus 5 4 which was manufactured by LG and to date that was the worst phone I've ever owned. I guess my point is it doesn't matter who is manufacturing the hardware; if Google is involved it's gonna be junk.

Edit: it was a 4 not a 5 but either way it was such an awful experience I've never bought another piece of Google hardware since