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.