The game was near-universally praised for its writing, but it failed to sell well due to the advertising misrepresenting it as a generic modern military shooter (which may have been intentional). Its release was sandwiched in between both massive genre mainstays Modern Warfare 3andBattlefield 3 (the very sort of games it was deconstructing), which probably didn't help.
Several reviewers marked the game down substantially for its poor multiplayer component. As noted elsewhere, Yager Development had no wish to include this component, and it was developed entirely by a separate studio. It's possible that had it not been included, reviews would have been more positive and hence the game might have sold better.
Banned in China: Due to the whole "Dubai left to rot" premise. The finished game makes it even more understandable since the intel items reveal the Emirati government knew that the storms were coming and had the wealthy evacuated in secret while ordering the media to cover it up.
Creator Backlash: According to the writing team, multiplayer was mandated by the publisher and farmed to an outside studio for development. Lead writer Cory Davis describes it as a different game entirely, "rammed onto the disc like a cancerous growth."
Made quite obvious by the fact there is no achievement for multiplayer, and that many of the achievements of the game that would seem to be easier to get by playing multiplayer can only be unlocked in the campaign. The dev team is basically telling us it's not meant to played.
Williams: This would be hard enough to experience just once. But, writing a project like this takes time. About 3 years, to be exact. That is a very long time to be immersed in a game like Spec Ops. There were definitely times when I wanted to walk away from the project, because it was taking a serious toll on my life. But in the end, I couldn't walk away from a story and project that was so personal to me and the team at Yager.
Enforced Method Acting: According to Word of God, the voice recordings were done with the entire cast together in chronological order, so that by the time the end comes about the cast members were tired and angry and just ready to go home. Sort of like Walker's team.
As a result of the poor multiplayer mode, several reviews marked the game's score down significantly. According to the lead designer, the multiplayer mode was done by another team entirely on a publisher mandate.
In a positive example, 2K Games stipulated that the game was to be a military-themed shooter set in Dubai long before the actual game went into development. Writer Walt Williams has stated that he appreciated being given this "box" to work in, as it forced him and the rest of Yager to be creative in how they designed the setting and narrative.
According to this article, which Williams contributed to, the reason the entire framing device with having the helicopter sequence, in the beginning, is so odd and barely acknowledged is that it was a last-minute change by the executives while they were recording dialog.
The story was originally going to be an even greater homage to Apocalypse Now then it ended up being. According to Word of God Konrad was going to be like Colonel Kurtz conducting illegal search and destroy missions in nations that the US was not supposed to be at war with. In the same way, Kurtz was in Cambodia and Laos, Konrad would be infiltrating Iran using Dubai as a base of operations. The U.S Government would then send Walker to assassinate Colonel Konrad and terminate his command just like Willard did to Colonel Kurtz. This was changed mid-development so that Walker would simply be sent to conduct recon on Dubai, with Konrad actually trying to help Dubai.
As noted elsewhere on this wiki, Yager Development had no desire to include a multiplayer component in the game, and have openly criticized its publisher-mandated inclusion.
Several members of the team (including writer Walt Williams here) have stated that they would have preferred had achievements not been present in the game, as they thought they detracted from the emotional force of some sequences. In the end, all the achievement pictures used in the game are pictures of the developers mocking the player.
At one point in development, Josh Homme was attached to compose the game's score.