As a user, I usually can't even tell when they're using a polyfill on the web (except when they stop, like GitHub did with type=date). (As a developer, I often can't tell the difference, either. Some of them are that good!) So long as you generate HTML/CSS/JS, it doesn't matter to me how you do it. That's as 'native' to the web as you can get.

I can spot Qt a mile away. A lot of the visuals look wrong and a lot of the controls don't behave right. It's frustrating to use, and I always slow way down and double-check my work because, e.g., popup menus show the 'accept' animation even when you cancel them.

You mean it has no respect for your native toolkit... just like the web?

How true is that? I was under the impression that for Android and iOS, Chrome used the native widgets for most things.

There's no scenario where I only have to write two native apps. Perhaps there is for other people.

You're a hammer, so everything is a nail. The reality is that the web is a horrible choice for a whole lot of things. It's a document platform with parts of an application platform shoe-horned in and bolted on, and the result looks like a garbage fire to people who come from the land of native software.