You can very easily have aged based/birth year elite level lacrosse teams.

They already do that is elite soccer , ice hockey and basketball in this area.

Most rec or second tier programs have the blended ages

Soccer plays the same amount of games if not more then lacrosse in this area and they have plenty of fields and officials.

I having youth aged kids play against other kids that are the same birth year provide for better games and player safety at the elite level.

Once in high school graduation year teams are better for college coaches so they can see players who might not be playing alot as a freshman or Sophomore.

Plus once in high school you cannot hold back do to Maryland High school sports rules.

Personally I do not have a problem with a 1 year hold back but when you have players who have held back twice that is problem.