But I agree with your core point. I use VS Code all the time, regularly switching between maybe a dozen different projects, and I personally don't run into performance issues or resource constraints very often. Certainly less often than with heavyweight IDEs like IntelliJ, Eclipse or XCode. But I felt the same way about Atom as well, so maybe my typical project/workflow/usage pattern is less resource intensive than others. (For one thing I hardly ever run apps from _within_ the IDE, I prefer to build/test/run from a terminal, so that might be a factor.)
VS Code isn't quite as responsive or quick to start as something like vim, or even emacs when run in a terminal, but its resource demands seem roughly on par with any other feature-rich IDE/editor in my experience.