I've found there are various gradations of WordPress developer and the "pro" guys are a very competent and very pragmatic bunch.
- Most "pro" guys limit the number of plugins they use.
- They use ansible or similar for provisioning and deployment.
- They use sane theme frameworks like sage, timber or stem.
- They know how to do caching without using clunky caching plugins
- They try to adhere to 12-factor where possible
- They do their own devops
I mainly consider myself an iOS/Cocoa developer but I do my fair share of web development including WordPress. I even sell a pretty technical WordPress plugin (https://mediacloud.press). I don't recommend or choose WordPress because it's a great platform, but because it can be a solid pragmatic choice considering all things like time and budget and client experience.
But for the average joe, it sure provides plenty of ways to shoot yourself in the face. That said, what other options exist for them if Wix isn't enough?