Agreed - too may who competed hit their peak with that meet and were hardly heard from again, with some exceptions of course.
The Junior meet (labeled U20 now) is enough as very talented Youth aged athletes can also compete here.
Heppenstall competed at the Junior meet in 2014 as a Youth -aged athlete. he moved up to Pan Am Jnr (podium) the next year (2015), then to NCAA finals (indoor and out) along with U20 final this year (2016) in his last year as a Junior. This should be enough to foster a proper Senior career - no one has to be great at 15/16 in order to be a success later.
I think winning at the Youth level can be more a curse than a blessing, and confers pubertal advantages that really shouldn't be recognized. While Bolt won as a Youth (2003 Sherbrooke), was it really necessary for his long-term development?