I think gamers expectations have kept rising as time goes on, we expect better graphics, better mechanics etc. The problem is that we're not willing to pay more for these things, we expect games to get better but not cost more, which is challenging for developers to cope with as they need to pay more for employees, office space etc. and as the market has been flooded by lots of different titles, gamers are fatigued with the amount of choices they have, and in the end it becomes much harder for a developer to sell their games to a large audience, especially AAA companies who rely on lots of people in the "mainstream" market buying their product.