OP brings a very valid point in his first point, the online part sucks. I have barely seen any comments about that part at all.
. Which leads to point #2. In the absence of a decent Multi-player experience, the game is looked to for its single player accolades.
Note how he points out that he only considers singe player to be a problem due to "the absence of a decent Multi-player experience".
He's absolutely right about the second part as well. This game is mainly considered to be a RTS, with elements of a 4X game in it, not the other way around (check Wikipedia, or any major gaming sites like gamespot.com). It's only natural to assume that just like every RTS I've ever played, it should come with a campaign mode. There hasn't been anyone who has asked to get an entire singleplayer campaign mode patched into the game, but there has still been plenty of posts explaining why that would be stupid in a condescending tone. It has just been stated that with a bad online experience, the singleplayer part will get even more focus, and the only singleplayer game there is, is sandbox.
The issue with the lacking single player is only an issue because the online client is so bad. This should have been fixed before release, and the best way would be to make sure that the online client worked properly.
Sandboxing might work fine for the 4x fans, but the RTS part is atleast as prominent as the 4x part (I think the RTS much, much more prominent but I'm settling on the middle to be somewhat diplomatic), and it's only natural for those who are used to RTS games to react on this.
tl;dr: Fix the online experience, and the need for something more than playing versus the always boring AI will be satisfied for most gamers.