I'm fine with my on age kid playing against holdbacks. Good players play up, not down. Simple way to solve the holdback issue, and it doesn't take reform from U.S. Lacrosse, just a little transparency from HoCo.
Every HoCo team should have to submit a roster that includes birthdates of each player. Post that info - no names identifying kids - just the D.OB. and zip code for each player on the team on the HoCo web site. Then everyone would see what teams are really 'elite' and what teams are just stacking their rosters with holdbacks and double holdbacks.
I do think it is a safety issue when certain clubs with anger issues use 5th graders against 3rd graders. Publicly posting D.OB. info would be a free, easy, no cost way to at least level the factual playing field.