I think usability almost always suffers when the native UI isn’t used. It’s not that platform-neutral UIs aren’t usable, or good looking. However when native UIs were prevalent, there were standards built up over years of hard-earned experience: for a Windows app, you wanted to get your tab order right, and you knew the convention of getting the Cancel button mapped to the escape key etc etc. See also the Mac and the HIG, encouraging apps to look and work roughly the same.

There were always outliers and ugly UIs, but it always felt like there was a uniformity that made it easier to get around in an unfamiliar app. Whereas now, electron apps look and work very differently (comparing slack to Spotify to VSCode and so on).

That said, I think very few people care as much as I do about it, and cross-platform UIs save a ton of development work.

Not only usability, but also raw capabilities. Most native toolkits handle UI and basic ux well and has good interoperability with system components. With most cross platform frameworks, the developer is often reimplementing these or trying to resolve platform incompatibilities (always badly). And the project quicly balloons in complexity.

They’re great to get started, and when what you need is already available. But they’re a pain for everything else.

Part of my curiosity was sparked by the article on HN the other day discussing the hamburger menu icon: it used to be confusing, but now is pretty widely recognized as long as some guidelines are followed. So while I used to agree with you re: usability, these days I'm not so sure anymore.

One idle thought I had: when computer interfaces were still new, using physical analogies like file cabinets was good practice for teaching new users. Maybe GUIs are now commonplace enough that people are able to speak the different "languages" without as much trouble.