All those clamouring for offline with game as is are kinda missing the point I'm afraid.
You cannot release a rubbish and empty product and call it offline. Anyone who reads game reviews on a regular basis knows how much crap you get if you release a shoddy product, whether it's offline or a single player story mode.
On top of it the missions and actions of the AI are pretty reliant on the evolution and simulation. Without it, nothing happens. You as a single player simply do not affect the game enough.
It is static, lifeless, void of anything to do other than dabble with some of the mechanics like trade and mining. But there is precious little you can achieve.
Yes its a design decision, but one with serious technical and development costs associated. It really isn't a "it won't be true to vision so scrap it", but much more a "woah it seriously won't work at all well without serious more development time" and at that point it's better off as a new game or heck, maybe. A later expansion, who knows.
What I do know is that there are legitimate reasons for people being upset and there are IMHO flawed ones. But clamouring for a release of some empty lifeless void will not happen. You think the press made anything of this? Try what they would do if offline mode was released as some of you have suggested, for what? To placate a few? Take the rep hit and refunds now and release a quality product.
Am all for debating the rest, but the idea of any form of offline release of current build is an understandable no no.