Maybe tell us exactly who you are and the club involved and the person who took your place...that would make this a whole lot easier to debate. At the moment, its pretty hard to get the whole picture.
Generally, if you are good enough, you will play. Simple, doesn't matter what age.
As much as people like to call it deveolpment, in the end I have never met a coach that does not like to win and therefore have never met anyone that coches at senior level who does not play the players that he thinks will give the team the most chance of winning. So, although people might think that the coach is playing a junior to further his/her deveolpment, it is more likely the case that the coach actually thinks that the junior will give the team more chance of winning. Now, sometimes the coaches get it wrong, which makes it look even more like the junior was played for the experience, when actually thats not the case.
The only way i can see a coach playing a junior who is not quite up to the standard as the seniors playing, but still plays ahead of the senior is if that teams season is shot and they can't make the finals and the coach has lost faith in the current playing group not just to succeed this year but in years to come and so, like Richmond in the AFL have done, decide to go for a youth policy. Which I suggest maybe Southern Tigers mens ABL coach might want to think of doing now! Seriously, how bad are they! At first I thought that they were just not jelling, but I have come to the conclusion that they just are not any good. I saw them get flogged by th eagles on the weekend and it wasn't because they didn't try, or they got a bad deal from the refs or because they had a bad night or anything other than they just didn't have anywhere near the talent. Clark, Goodenough, Bowley, both Hodges, Francheseanes...here are 6 of their top 9 players who would not play if they were on one of the top 3 sides playing lists. I'm not talking wouldn't play much...I mean would not play at all! Unfortunately their younger players are pretty crap as well. Good luck with this group Heath...your going to need it!