As a small anecdote as someone who switched from atom, the killer feature for VS Code is being extendable AND performant. I used to use atom for a flexible text editor, and then still have to use sublime text if I wanted to open a large file (atom choked on multi MB json files).

I don't know if it's possible to get the performance you need to make an IDE/text editor feel snappy in most situations with a pure DOM solution.