Are you guys actual programmers? What's wrong with using Vim for development?

What do you mean "build our dev environments around vim"? If you mean they write dev tooling in vimscript and explicitly require everyone to use it, I actually agree with you. I don't believe employers should really ever force any particular editor or IDE if the work is getting done. I would be equally annoyed by a workplace forcing me to use vscode instead of vim. It would slow me down way too much.

If you are just complaining that they build dev tooling as a CLI, hard disagree. That is absolutely what dev tooling should use because it's actually universal and can be used regardless of your editor choice.

At my workplace, our dev tooling is done via CLI and our developers use vim, emacs, and vscode. Because it's all CLI, it's easy for individual developers to add their own scripts to automate parts of their workflow as they see fit (and if such automations are deemed useful by the group at large, it will get merged into our shared devtools repo). We even have some editor-specific stuff in there people have written that they find useful, but it's entirely optional.