While Maybin had some injury issues in 2016, he actually put up some strong numbers in 94 games. He had a .315/.383/.418 batting line with 4 HR and 43 RBI. He also had 15 stolen bases. While he wasn't an asset defensively, he was still a very useful player.
Alcantara had a pedestrian season in Double-A, so on the surface this trade doesn't look very good for the Tigers. Apparently, their scouts believe in him and the Angels definitely could Maybin in left field. This isn't exactly selling high, though. It looks like the Angels made a really good deal here, although they will be paying him $9 million. The Tigers really were just looking to clear payroll here and get an arm with upside. If he provides the same kind of value in 2017, though, he'll be well worth that paycheck.