Yeah indeed chromium is a more efficient 2D rendering engine than what's available natively and performance of JS is comparable to Java. Electron apps being slow is mostly a developer laziness problem, not a technology problem. Making a fast electron app is actually easier than making a fast C++ app IMO, when you take into account the libraries and tooling available.
I think the difficulty is in making a lightweight Electron app, not a fast one. Games run fast too, but they can get away with hogging resources because they're typically the only app you're using at the time.
