[QwertyPi]

That seems to remove the advantage of using the browser in the first place—leveraging native controls and integrations, giving the user control over how things are renderered, and accessibility concerns.

Of course, I can see how this is mostly irrelevant for some applications like games, but that's still rather niche compared to, you know, useful and wide-spread apps that people actually want to use.

[modeless]

You forgot about the most important advantages. True write once run anywhere cross platform support, and one click zero install distribution with no gatekeepers. The latter in particular is key and impossible to replicate any other way because device gatekeepers like Apple or Nintendo will never allow any other app platform to bypass their distribution monopoly.

[QwertyPi]

> True write once run anywhere cross platform support, and one click zero install distribution with no gatekeepers.

We had (have) that, and the apps were miserable to use for the same reasons enumerated above. The place where it has come closest to succeeding? Video games.

Unfortunately, platforms are too diverse to target as a generic platform without making major sacrifices as to either consistency or usability.