Because VSCode is an electron app, meaning that it probably relies on Chromium-only features that they have to find workarounds for in Firefox before things lik

Because VSCode is an electron app, meaning that it probably relies on Chromium-only features that they have to find workarounds for in Firefox before things like keyboard shortcuts work. Keyboard shortcuts are probably important to people that want to transition to this, so instead of saying "Firefox works, but not nearly as well as Chrome", they said "Firefox doesn't work, but we're working on it to make sure it works as well as Chrome". Also, the next major version of Windows will ship with a Chromium-based browser by default, so they probably didn't care about prioritizing it as much as making sure Chrome worked.