It's a travesty against the entire Marathon series to make it a slop-of-the-quarter extraction shooter. Durandal despised humans for this exact reason.
It is difficult to get people to try an extraction shooter. Not really the most popular genre of FPS. More so when you don't have a single player campaign. If it was F2P that would help the numbers a lot, but Bungie needs to make guarenteed money on each player because the 250 million dev budget.