I do think it is easier in individual sports where level of competition can be manipulated much easier. Or in sports where size and athleticism matter more (e.g. Dkembe Mtumbo could pick up basketball at 17 and become an all star). But the theory of focusing on skill development, hard work and having fun without crazy national circuits for as long as you can has a ton of merit.
Our son’s first coach had a local team with 5 D1 players with his older son. After they won Cooperstown they all got poached by national teams who played “the circuit” spending way too much money traveling and playing in high profile tournaments. Learning from that, Coach Goodwin pledged to keep my son’s team together for as long as possible (as long as the kids wanted) to avoid the business of high level travel baseball for as long as possible and to keep it as fun as possible. He created the best competition he could within that setting—son never played in PG/PBR/etc. event or showcase until HS. The boys are still in touch and range from players in JuCo (1), D/MiLB (2), D3 (4), 4H judge (1), chef school (1), amazing members of the regular student body (4). It was a very healthy baseball hybrid and allowed each boy to figure out his own appropriate trajectory when the time came.
Once in HS, I do think playing against the best competition you can (that stretches you without overwhelming you) prepares you for what’s next.