You and I both know that one person can write UI in a vacuum, but there's a litany of other challenges that come up when positioning an application across platforms - sharing code, resources, etc. If all you look at it on is a technical level, you're doing the problem a disservice.
It's not that they cannot afford building 10 native AppleTV apps in parallel and pick the best one.
Call me when Microsoft actually ships WebView2 with the OS.
"This is literally what Slack moved from years ago, because it was very problematic, let me tell you why since I'm the one who did it.
* Adding new APIs was a huge pain in the ass, you had to write all of this ugly bridge code in Objective C, and the APIs ended up being super unnatural on the JS side. As a result, desktop integration wasn't done much since it felt like a "Black Magic" type thing. Writing new APIs in Electron is Just JavaScript, so you can make something much more natural.
* We could literally do fuck-all for people running old versions of macOS - you can't upgrade Safari on old machines, you just Get What You Get. For awhile, every YouTube video on older macOS versions had a pink shade to it. Users write in, "This is clearly wrong!" "Yep, but we can't fix it. Sorry."
* And big spoiler - WKWebView uses _basically_ the same amount of memory give-or-take a few MBs as Chromium. It's the content that sets the memory usage bar, not the host. "
Coincidentally, Slack doesn't fully work in Safari or traditional Edge. Video calls only work in Chromium-based browsers, and in the Electron app which is of course also Chromium.
This is actually the thing that finally got me to switch back to Chromium last week, after using Safari and Firefox for the better part of a decade. The Electron app sucks, I don't like switching between browsers for usability reasons, and I need to make Slack calls for work.
For example, Slack-the-Electron-app and Slack-the-web-app are fundamentally identical, aside from likely some platform integration features and so on. That means that, likely, a lot of these Electron apps would already work in, for example, a Safari or Edge webview, since the web version has to anyway. I sincerely doubt that they're taking the time to strip out that compatibility, since the only reason to do so would be efficiency and if you're using Electron that's not a priority.
IOW, for many applications, there's a near-100% chance that everything would function with little to no extra work, and for most of the rest it would likely take very little.