I would quit so fast if my company forced me to use a web IDE.
GitHub isn't forcing anybody to use a web IDE. The most broadly used access interface is VSCode. Then there are heretics like me who choose to ssh in so we can use Vim. This is described in the article.
Do you have to drag your .vimrc and plugins along every time you set up a new code space? My vim setup is pretty bespoke, it would be annoying to have to set that up every time.
I once had a setup where I could just clone a repository and run a script to get my dotfiles set up. For Vim, I would just need to then run the command to install the plugins and that was that.
Edit: Here is the CLI program that helped me set this up: