Aside from update frequency you wouldn't, users can't tell the difference if it's done well. Are we not talking about "the state of software development"?
Huge companies, yes. They'd still prefer to spend less money/resource/time if they have the option to though, hence why some large companies actively explore cross platform technology. Adobe did that with phonegap a long time ago.
You're talking about Electron there, which like phonegap is a browser wrapper and a different thing to RN. I don't believe RN is known to be a battery drain in general.
Badly, which is why we have a totally different approach in the form of RN, Flutter etc. The concept of cross platform support wasn't the problem, that's what we're chasing for a reason.
What are some well done cross platform apps that don't unnecessarily drain battery life? I can think of one - VSCode.