I think it's better to understand the difference between choices and rules: 5e has fairly easy rules: if you take the starter set box rules, the player facing rules are almost the same of the PHB, and are easy. DMG rules on DMG book are not so many either.
I don't think people want more complex rules. People, IMHO, want to create characters based on many choices. And those can be added in non core books.
Am I wrong? Probably yes. To me, the perfect way to sell 1D&D would be a starter box like the red box, then books for expanding it to higher tiers. As I said in the D&D movie thread, WotC needs to create a complete not expensive game that is a just a box for the dungeon delving. Wilderness, Dominion and multiverse? Those are books that expand the basic game. It would cost "more" for groups to get the complete game, but if you want just a part of it, it wouldn't be the 150$ of the complete core set or the 20$ of the demo (because starter and essentials are demos, without tools to make more dungeon or adding dm tools for beginners)