Yeah, I should have said when they launched up the divisions in the 2000's (this was at a time when everyone had juniors), but Rowville went like a train from Div 4 to Div 1 and had something like 3-4 teams at each level of juniors at the time (about the mid-late-2000's).
It's just not going to be a thing that Alexandra or Yea will be able to fly up to Premier for a sustained period, or that Pakenham or Narre would slip to Div 2. Demographics are immovable objects in local footy.
You are correct in that Rowville had an enormous junior set-up around 20-odd years ago that has served them well, however that successful senior side also had a lot of external recruits, so getting to the top of a league like the EFL isn't just about demographics. 20 years later and Rowville is a mature suburb and the growth has gone further south. Things change so it'll be interesting.
Agree however that many of the old YVMDFL clubs are simply country towns and aren't changing. The OE league was a doomed experiment from Day 1.