You are claiming a false dichotomy. Specialization doesn't mean future-deprecation. Every single cross-platform app is written to an abstraction. There is no implicit assumption that all abstractions are good. Whenever I hear cross-platform code I think slow bloated web-apps or slow bloated java apps with a funky UI.

Websites written for IE6 can still be used today with minor changes. The problem is activex and other crappy plugin technologies. If people had just targeted Win32, those apps would still be working today - but probably still end up requiring a rewrite because of modern security requirements.