It's often easy to tell, but my concern has shifted from "Why isn't this native? It's ugly/slow" to "Why isn't this a goddamn webpage? It can't justify neither its permissions nor its space".
from the comments:
> Definitely every one of these is sluggish at best on a very modern machine but they are also full of UI annoyances.
On mobile the webview app experience is crap and it's immediately obvious that an app is not native. Simply nobody asks customers how they like it. The management assumes that as long as nobody complains and the users don't leave in droves, the experience must be impeccable.