I don't really see the academy as breeding ground for "stars", though. Not when we're talking about English/Irish players anyway, as they'll only ever be as good as the national team they might end up playing for (i.e. in recent years, not very). If our academy can keep churning out decent squad players that's still a valuable resource. In terms of potential stars, they're more likely to start their career in another academy and move to United when they're a little older. Januzaj and Rafael the most recent examples. Pogba, Rossi and Pique also being relevant. A pity their careers turned out the way they did but still reflects well on our academy that we "produced" them.
This might change if the quality of English player being produced in general is on the up. Liverpool have Sterling and the careers of Wilson, Rothwell, Mitchell and Pearson might follow a similar path. Time will tell.