There are options that let you write the bulk of your code in one language then code platform specific user-interfaces against that library. This is basically the Xamarin philosophy for iOS/Android development, and Xamarin apps generally offer a much better user experience than these web-app wrappers cluttering the App Store.

We were talking about desktop apps in this case. It's slightly different on mobile but the parameters are similar. The range of options here involve fiddling with dials that affect cost and quality. The comment I'm replying to amounts to 'why not pretend these dials don't exist?'. The answer is, because they're really there, you can't effectively plan development like that.

Yes. It's typical for a team to have different people handle different platform and spreading task on multiple people suddenly slows down the progress than letting 1 set of people handle the front end.