What do devs who don't use VSCode do to work in this environment?
Not sure how GP's company does it, but that is how I would configure it.
Caveat: the default devcontainer initialization workflow does _not_ create the Dockerfile, only the .json.
At $work we don't use devcontainer.json, but we can launch the development environment image such that you can SSH into it as if it was a regular VM.
I dont actually mind what development environments our devs use, as long as your productivity is up and you get the job done and you are happy. You can use a magnetised needle for all I care, whatever makes you the best version of you.