In my opinion High School works for football, baseball, and basketball... yes. Most of those successful programs have kids playing year round, plus

Football in the upstate have dedicated weight training classes blocked out for the last period of the day...football players only
they have dedicated strength coaches...
they have 100,000 coaches...
they get fired if they do not win enough...
they want to win football games... if you do not believe me read the Palmetto football sight and all the talk about firing coach Brown at SHS... with an 8-3 record

how many high school soccer programs can be described in this way?

how many european clubs could be described in that way?
Probably more the later than the former.

We know what to do, but will not do it for a soccer team, across the US as a whole... until then we are toast.