Stansted indeed has superb infrastructure, especially airside, it was build in an age and by an organisation where there was little incentive to skimp on investment.
Given that MAGs finance costs are pretty set they are left with three other routes to achieve their forecast return on investment - traffic revenue, commerical revenue and operating costs. If the Ryanair growth is delivering little or no additional traffic revenue (as is generally believed in the airline world and also suggested in the annual accounts) and they have already done as much as they can to boost retail income then this leaves the cost base as their final recourse - if cost budgets are under pressure then that would explain the obvious lack of resource, and I would wager there are a few very stressed line managers in the organistion right now who deserve every sympathy.