AHL is tricky compared to those other two leagues. (IMO) The other two leagues are FILLED with younger players who don't have the plethora of other decent leagues to join (while young). On top of that, there are guys that are fringe/capable NHLer's that actually don't ever come across. They hold top talent a little better, and imo, players playing with more talented players develop their own game better.
In North America we've got lots of competitive semi pro, juniors, then the NCAA even. Most of these guys that can't crack the NHL will settle in the AHL, older around 22years+ old, kind of creating a stagnate pool of talent in their league with older players. Anyone really good will only be there a short awhile and long-term players will only be so good, and only so skilled. Example, Taro Hirose.
For most prospects, imo, it seems to be the league to see if you can stand the physicality, space, face-offs/special teams, and speed before the next bump up. Trying to draw up a younger players actual skill, skating, vision... idk if the AHL is the right league for someone like that to step into. Outside of goalie. Most younger players need to be a little polished, imo, stepping into that league with men that try to hurt you.