And that the very simplest examples have to download 12MB of code before they can do
anything. (OK, so it’s probably more like a 4.5MB download. Still waaay bigger than you should require for most purposes.)
And you don’t seem to be able to enter astral plane characters at all (though that’s just an implementation bug that they haven’t dealt with yet, and shouldn’t be a fundamental problem of the approach).
And controls are all wonky and non-native in look or feel. And keyboard control slips badly in many places so that you lose your place within the window easily.
Recompiling desktop apps to the web (and specifically Qt, but also excluding games, which live somewhat in a space of their own) is very niche.