I think the major issue most of the managers have with shotblocking is that it is an "invisible" skill as the output does not differ much for players with low or high blocking skills - instead you clearly see the better production you can achieve with a player who is trained in IS or Reb.
Also it is quite unimportant which position a player play for blocked shots - my best blocker was a SG, he even holds the record for blocked shots in my old league. thats not realistic, something has to be tweaked there too, imo shotblocking could be a perfect skill for guards if there is no difference in blocking outside or inside attempts.