Yes, iOS is a glorified App launcher. There is nothing else to it. And while the Apps are important, Apple can't rely on just them forever.
All operating systems are, among other things, "app launchers", so apps would be better characterized as "fundamental" rather than "important". Apple will rely on apps forever.
Operating systems manage the interplay between apps, multi-tasking, hardware and so forth. An OS without apps wouldn't do anyone much good. A good OS user interface (what's really being talked about here and is the set of applications on an OS which manages user inputs) allows users to get on quickly and efficiently with starting/stopping/switching applications or making configuration changes. iOS has some opportunities for improvement on the "quickly and efficiently" front. Customization would be nice. Not sure, as others have suggested, a radical rethink is needed, just some tweaks.