What is the problem with SE5?

[Moriarty]

Without a lengthy discourse as to the nature of the problem what is the ONE problem you have with SE5? The one and only one that eats you up more than any others?

Simple answer: "death by a thousand cuts". That's the one reason. If you want a comprehensive list there are a bunch of threads that cover those.

Uncle_Joe: I remember them pointing to a poll that they conductd on THEIR SITE about wanting multiplayer or not. They said the results were overwhelmingly against. Well, if you ask on a SINGLE PLAYER ONLY forum, its not likely that you will terribly many MP players hanging around to participate in your poll, are you?

A valid observation, but look at it another way - If they're content with their current, single player market, and that market has no interest in multiplayer, why do they need to implement multiplayer? Sure they'll get more players but they'll also gain all manner of troubles (both from a design and support perpsective).
I did see the poll in question and multiplayer lost by a long way. Also I believe this was for an addon. Who better to ask what you want in an addon than the current players?