The bigger problem is the use of dynamic HTML for UI everywhere. It'd be slow even if you used C to drive the dynamism, although having JS there doesn't really help.
As far as VSCode being a "snappy" Electron app - I still vividly remember that bug when users were seeing it hog an entire CPU core for itself while not being interacted with, and it turned out that it was caused by blinking cursor in the editor. You know, the kind of problem that was already solved by the time Windows 1.0 came out? And sure, they fixed it... but every desktop Electron app is a potential minefield filled with stuff like that. Some of it is just not obvious until you run it on slower hardware. Or in remote desktop - that also flushes out a lot of "GPUs are fast enough, who cares" problems.
As far as VSCode being a "snappy" Electron app - I still vividly remember that bug when users were seeing it hog an entire CPU core for itself while not being interacted with, and it turned out that it was caused by blinking cursor in the editor. You know, the kind of problem that was already solved by the time Windows 1.0 came out? And sure, they fixed it... but every desktop Electron app is a potential minefield filled with stuff like that. Some of it is just not obvious until you run it on slower hardware. Or in remote desktop - that also flushes out a lot of "GPUs are fast enough, who cares" problems.