What about a dumb phone ensure that call quality is terrible? Could you not have found a better dumbphone if you really wanted to stay with it?

I spent some time looking. There were some pricey "designer" ones, but they generally got poor reviews. Maybe it's easier to do a design-school exercise, than to get the phone guts engineering right. Also, mandatory VoLTE eliminated a lot of high-quality legacy devices that would've worked fine.

Why not consider a smart phone that has good hardware, supports VoLTE and doesn't use Android or Apple? I've been daily driving a Furi FLX1 for over a month now. You can make it as smart or dumb as you like and you can even use it to charge another phone!