Exactly. I for sure would've thought this would be a "20% time" app as lockdowns became common. Wyze figured out how to allow its security cameras to be used as webcams in March 2020! https://www.theverge.com/2020/3/31/21202022/wyze-firmware-up...
Phone as webcam just doesn't seem like a long term solution, eventually built in webcams will be cheap and good enough. And tbh I find the built in one on the macbook to be bordering on good enough once you consider how compressed and tiny the output will be on the other persons screen.
Apple actually did come up with a good solution for mounting the phone. A small disk that connects to the iphone with magsafe and has a flip out tab that can hook on to the top of the macbook. It's surprisingly stable and nice.
We've been waiting what, 15 years for this to happen?
I ended up getting a Sony mirrorless for a webcam. (Might seem like overkill but I spend a good deal of my time teaching in front of a camera.)