Why can't you use vim and VSCode? I use the neovim extension for VSCode[1] and it works great! That gets me real vim input and the VSCode extension ecosystem.
For me, a major reason is the pervasive spyware baked into VSCode. A lot of the code I write are things I would prefer Microsoft and the US military-industrial complex (of which MS is a big part) not have any data about.
The point of using something like VSCode is access to all of the features enabled by proprietary extensions. VSCodium has none of these and goes back to being worse than vim.
Microsoft is just engaging in open source cosplay when they publish the source code. They’re not interested in software freedoms as a concept (in fact, they are interested in explicitly denying them to users) and they certainly aren’t interested in enabling software freedoms via their releases (source code or otherwise).
Everything I've wanted works in vscodium. The only thing I couldn't get working is the remote sharing where you can connect to someone else's instance and co-edit (remote ssh editing works).