If we agree that this is a useful approach to take for developing cross-platform applications, and I think it is for most, are web technologies the best way to achieve this or is there a better alternative?
Web tech has the advantage that when you don't have that "game engine" you can still run in a browser, but with these engines getting better, more storage, more use of app stores, and the fact that these apps are very much that, apps, and not publicly indexable web content, maybe this isn't a useful advantage anymore? Web tech also brings a number of disadvantages, such as a different security model and unnecessary legacy compatibility that holds back modernisation.