Most questions currently are of the type "Recommend me an app for this", "Alternatives for X" and so on as you said.
I think it has a lot to do with the way the question is asked: looking for a web app to solve a problem should not result in a community wiki (I verified on superuser and they don't transform those kind of questions in community wikis). However, if the question is of the type "list of web apps that do this", or something like that, then the question is not asked to get a definite answer and should be made a community wiki.
I think this problem might be because of webapps is relatively new.
Whenever we see a question that doesn't quite fit the mold for a "real" question, I suggest a rephrasing of the question first instead of automatically asking to flag it as a community wiki.