Code is not a fast editor, and you're right that this is likely linked to Electron, but I do think lumping it in with Atom is possibly turning many off it too quickly. The gap in performance between Atom and Code is phenomenal.

It's also worth remarking on that some of the treatment of these two in this article is a little odd. Atom is excluded from a lot of tests completely, and Code is particularly penalised in one test for incomplete highlighting (where it's noted it completely the functional task "quickly").