I think there's a few things that hold quality back.
1.) Money
Planet Earth is broke, most production requires large sums of money and not even all of it is actually sunken into the quality of the product because you need things like advertising, servers and so forth.
2.) Demand
Why make something truly amazing when standard/decent will net you just as much, and you can keep the cutting edge stuff ready for when standards start to go up?
3.) Time
The greater the game the more time is sunken into it, so by the time it comes out it just feels standard by then instead of amazing.
