From my experience, academy players are useful (usually have good form). But I think they're geared towards token buyers. And by token buyers, I mean high end ones, which developers of these free to play games, call whales; those that drop say $100+/month on average or something like that, so such players have access to the greens to train em up.
Even so, a strong argument can be made that nordgens are a better investment than academy players. Haven't purchased enough academy players or nordgens in my t11 playing career to truly test the average effectiveness of nordgens vs. academy players, since I've only acquired two 24 academy players and get like 1 to 1.5 nordgens per season on average. One was rather average, the other has scored roughly 450 career goals for me so far.