This sport never grow to its full potential until USA lacrosse stops with allowing holdbacks.
I don't think that on-age or off-age makes much of a difference in the growth of the sport. What does make a difference may surprise you.
The Aspen Institute has been studying this for some time.
There is a growing belief that early participation in club lacrosse is resulting in a slowing of growth of the sport at the middle and high school ages. Kids who go out for lacrosse at school who have not been playing club find themselves at a significant disadvantage versus kids who have been playing for several years. In many cases, they see the competition and walk away.
See this article for more info: https://www.aspenprojectplay.org/state-of-play-2020/ages-13-17