With the success of Electron apps (i.e. Slack), I am starting to think this level of OS/GUI Fidelity isn't all that important. As long as the application is attractive and does the job, people don't seem to care that much about it matching the OS look and feel.

This is a very common misconception these days, IMHO. "Because people just use best of what's available, I presume that they are actually content with what they have." Today another thread talking about web apps and the heaviness thereof, people suggest that given people use these apps/websites, they must really prefer these slow, messy and creepy things to plain, information-dense sources. This might be indeed true, but you can't conclude so just observing the status quo from outside.

instead of "best", I'd say people use what's good enough. electron is good enough for most people, and some people do notice the high resource usage, but they are in the minority, as most users don't attribute sluggishness of the machine on the app that's not slow (and electron can be made to feel fast if you know what you're doing).

Electron is not "good enough for people" because people don't know about it, or, to put it better, are not supposed to know about it. It's an implementation detail.

> sluggishness of the machine

So say a machine with 4GB ram and a decent 4-core CPU around 1.8 GHz is sluggish? Let's honestly say "we're sacrificing resources on the client side for ease of development on ours".

I wouldn't pin the success of any app on Electron. Most would gain a lot from pivoting away.

Take a look at this article http://www.red-lang.org/2017/07/063-macos-gui-backend.html and see the info about rule-oriented rewriting engine that actually tries to deal with such differences. It's of course not perfect (Red is still in alpha), but it's not something that's being overlooked.

You can see how Red is starting to approach this in http://www.red-lang.org/2017/07/063-macos-gui-backend.html, particularly the Cross Platform GUI Metrics section. It is a really hard problem. Technically it can be done, if you put all the onus on the user. The more we try to do for them, the harder it gets. It will always be a balance.

Ah, I see @rebolek noted that as well. He always beats me.