Those tools have never worked. And for some reason, somebody at Microsoft really wants people to use them anyway. The first thing that everybody learned was to stay well clear of the drag/drop interface builder and anything that seemed like it existed only to support it. In 2001, that lopped off roughly 90% of ASP.NET and left one with a really nice platform for development.
It's actually surprising to hear that it has persisted all the way through to ASP.NET MVC and the new view engines. I hadn't heard of anybody getting bitten by it, had to advise anybody to steer clear of it, or even seen it in any version of VS.NET since 2007.
Apologies that the message never made it through. Don't use any of that stuff, and you'll find that the Microsoft stack is quite a good platform to build off of.
If business and the projected revenue looks sufficient then maybe you should get a technical co-founder. You could learn a lot from somebody with more developed skills.
If a technical challenge then maybe you need to improve your skill-set. Building an AppStore requires more than programming skills, you will also need design and UX skills, etc. The key is to choose a suitable framework and then learn the underlying language.
Also, if the technology is really holding you back then I would guess that you are not interested enough in the project. That you are considering giving up on the idea altogether is another tell. You can make anything work if you really want to.
Don't do drag and drop if you can avoid it. There will be problems with drag/drop, no way around it.
Good Luck!