I guess I'll take a couple whacks at the dead horse...
I don't think it's so much that he was terrible at it, since I don't think he ever earnestly tried to go after many of the top players in the area to begin with. I got into a disagreement with the owner of a certain other board who insisted the reason GW recruited poorly was because he was "lazy." Trust me, it wasn't because Gary instead thought it was more important to spend summers on the golf course or the beach. There's really numerous reasons that he didn't get better players.....from his dislike of the gray area that was recruiting via AAU, to his preference for experienced players (and thus avoiding likely one-and-dones), and his own personality. Gary always had a giant chip on his shoulder, and especially after winning a championship, he didn't believe he needed to bend over backwards to get a certain player. And more to the point, he didn't think a player that needed to be recruited in such a manner would mesh with his own underdog mentality, and would just be a poor fit in his program.
However, it should be noted that just before his retirement recruiting had improved. Gary signed Nick Faust, had a commitment from Justin Anderson (who decommitted when he left) and was close to getting a commitment from Shaq Cleare.
I think this sums it up perfectly.
Gary at age 66 decided that he was not going to kiss 17 year old one and done players butts. and more importantly deal with the sleazy aspects of the AAU coaches. He was not a terrible recruiter nor was he lazy but he seemed to draw a line in the sand as to how far he would go and what kind of players he would pursue.
Gary used to be buddies with Boheim and Calhoun but in the later years had a falling out with them over what he percieved as differences in AAU outlook. Good points in noting Justin Anderson, CLeare and Faust. They are all top recruits and probably would be playing for the Terps under Gary.
I refuse to bash Gary, because I think he was a great game coach who followed his principles in regard to recruiting. I will say he took kids that had no business playing at Maryland.