But that's the thing. Marvel is releasing these solo movies first for a reason. What you're saying might have been true if we had an Avengers film with no solo films before it, but that is not the case. Marvel wants the general audience to understand and relate to these characters and see these movies that excite them so much before putting them all together. And the "different stories" aspect is something that makes it more interesting. One of the main aspects of the Avengers is how they get along and work as a team. They are all very different people, and seeing how they cooperate and work together is something that has a lot of potential. Not to mention that the director, Joss Whedon, is great with ensemble projects.
Like I said, it's the first of its kind, and is no way a pathetic idea.