Budgets and cash are probably more the limitation, than the actual people available to work on it.
No, budget is not the issue. this game is released every year and sells at least 1 million copies. that's enough to pay everyone on the staff.
I think you might be over simplifying the process of making a game. (Even if it is just to build upon an earlier version like PES 2011-2012.) It is not as easy to create as a few people working on it...
i am not simplifying. Look at EA. how come they do a great job, but fail at gameplay? that's because they don't have the people to address that issue. (they are selling millions of copies, i know).
5 years! how many years do they need? There is no excuse.
This game is almost perfect. and improving sound will make it even more perfect. 5 years is not simplifying. it's laziness.