Maybe, but not for a graphics editor.

Slack hogs RAM and burns battery like crazy, and it's a bloody chat app -- as simple as it gets.

Now imagine an Electron version of Inscape with complex vector editing, gradients and co on screen...

It's not even very hard to imagine. Just go to any web-based diagram drawing service (there's plenty of that), and look how sluggish and crappy it feels even when performing simplest and most basic tasks. Now multiply that crappiness 10x for the complexity of vector drawings (100x if you're doing vector art), and additional 10x for the complexity of the effects vector formats can handle - and you'll get a ballpark of how Inkscape would feel if it was an Electron app.

I've used https://app.moqups.com/ for diagramming/wireframing for a few years, and it doesn't feel sluggish to me at all. Feel pretty snappy, in fact.

We don't have to imagine. Someone has made a clone of Sketch for the web: https://app.designer.io/. There's an app to download as well.

It doesn't match the performance of a native equivalent, but doesn't seem unreasonably slow or bloated either.

There are also two other Electron-based vector graphics editors on the app store:

- Boxy SVG - https://itunes.apple.com/us/app/boxy-svg/id611658502

- Vectr - https://itunes.apple.com/us/app/vectr/id1204645754

Can we tell without feature parity? I were writing such a webapp, I'd skip features that were slow.

The OP suggested that no web/Electron based editor could have "complex vector editing, gradients and co on screen". This has nothing to do with achieving 100% feature parity, so yes, we can tell. Anything else is moving the goalposts.

100% feature parity is a meaningless test in any case. Sketch doesn't have 100% parity with Inkscape, which doesn't have 100% parity with Affinity Designer, which doesn't have 100% parity with Illustrator, etc.