Earlier quoted context omitted.
Maybe so, but I have never seen a fast Electron app. VS Code, Discord, Slack, etc., all have awful performance on older hardware where native programs like the full Visual Studio fly. It's my personal suspicion that people cheerleading JS all are working with fantastic developer hardware, where the performance impact is pretty muted.
Part of that is electron itself - I've heard it carries quite a bit of bloat - and part of that is the DOM. The DOM is very slow because of the guarantees it makes. You can edit any part of the HTML at any time - by hand or by API - and everything will resize and reflow implicitly. That's an incredibly powerful yet heavyweight feature. If they're using React Native, the only non-native thing is the raw JS logic itsel…
But if an app does it "old school" then it can definitely be very slow.