If you want hours and hours of extremely tough Super Mario Bros., just go download and play hacks and patches. That's all you need to do. Since you're such an experienced game designer, why not make your own stages?
Nintendo has made a game that is a traditional Super Mario Bros. platformer. They've revisited just about EVERYTHING we loved about SMB 3 and SMW. Held items, increased difficulty, themed stages with unique properties, Yoshi, and more. They've added in simultaneous multi-player. Yes, it is about as long as those former titles have been, traditionally. Deal with it. That's the reality. If you don't think it's worth it, don't buy it, and send a letter to Nintendo about it.
Seriously, I'm glad Mario's 2D platforming adventures are back. I'll be buying the game and playing it with my roommate. I'll play the multi-player happily. And when I've beaten and completed it? I'll play it again. Because unlike other games, I've found I can revisit Mario titles more than once, partly because they aren't epic in length, partly because their stage design is refreshing, unique, and stays fun for years and years.
If you're not happy with that, I really think the genre isn't for you, and you want the game to be something it never will be. That's totally cool and all, but if you keep wanting that, you're not going to be happy, because it's not going to happen.