The problem here isn't the call quality, it is the customer service. This is typical Google. They might have many boffins working for them but they do not put the customer first and they don't appreciate the benefits of a customer first attitude. For a product that costs $$$ they should do it right, if they promptly dealt with customer service problems with real staff instead of outsourced 'ninjas' then they could turn customers with problems into their greatest brand ambassadors. In so doing they could convert a small army of people who prefer Apple but have ended up giving Android a spin into brand converts, spreading by word of mouth 'how much better Google is' and converting die-hard Apple fans into Google fans. But Google just don't get it. It is also cheaper to do customer service correctly than it is to have people left out there exasperated with the service they get.
Right now my sister is having trouble with their landline phone. They are cussing their broadband provider and blaming them. They have a retro 1980's phone that has 'always worked' but, after a house move and with a small child around, with unknown wiring in the new house it has to be the broadband provider that are to blame. Chances are that there is something wrong with the phone or the cabling inside their house. They are not willing to try a different handset (one with neat features like caller ID and no cord), they want to persist with the retro phone because it looks good, like the ones they grey up with. Sweet. They too have gone online and decided that the broadband provider are useless and that their services are off the mark. Yet there are many people with the same provider who have phones that work remarkably well, but, they have decided otherwise. Again, as per the Google problem here, there is a perceptual issue due to the poor quality of customer service.
Getting back to the Pixel 3, I had a phone with some stupid wallet style phone case that made it so I couldn't be heard on the phone. I was able to work out that it was the case and not the phone (or an app) but I too was grumbling about the quality of the phone before I realised that the problem was quite simple and had everything to do with the case and not the phone.
I wouldn't be surprised if the Pixel 3 problems were due to obvious but not so obvious problems in the majority of the cases and not some fundamental quality problem with the device. However, Google don't pick up the phone and talk to customers, they leave them to gang together on forums and make all their problems Google's fault, which it is. When will Google learn that in hardware the customer comes first and that customer service has to be done properly? It is such a shame as Google do put the customer first with their search and other software services, plus their design principles do a good job of embodying that.