Ours is pretty bad. Within my family we have 2 Pixel3 XL's (one recently replaced after blurry camera issue) and 3 Pixel 3's. All are experiencing pretty poor wifi calling, and not much better if we take it off wifi in my admittedly sketchy Cell area. We are on edge of small wooded area that none of the companies are interested in covering...but still within city limits of Dallas, so it's not like we are totally out in the boonies. We had some issues with Pixel 2's, but nothing this bad.
And then google assistant surfaced this article this morning. Apparently lots of people reporting problems. I am hoping this will lead to a software update fix....
https://www.androidpolice.com/2018/...lems-with-call-quality-and-connection-issues/
I love FI and otherwise love the Pixel 3.