There's been articles on HN specifically about how slow VS Code is, particularly the one about rendering cursor blinking, and of course anything running on Electron will never compete work the likes of vim, &c.

However, as Electron apps go, I've found it noticeably faster and less resource intensive than any others. Slack in particular is comparatively terrible, as was Atom in the past (people have said it's improved but I've not felt the need to try it again recently)