soccer actually does "select" for attributes, but over years from volume. some of the kids who start out good at select U10 -- juggle kings -- turn out so glacially slow they can't stay with the speed of play, limited help on offense, defensive liabilities, and are JV level by the end. a lot of central mids are distance runners and a lot of wingers are sprinters.
if you want to play an aerial game or defend one, some teams want tall forwards and central defenders. goalkeepers too.
if you weren't willing to be physical and slide tackle my select team would wash you out.
you don't think about it at the time but the unathletic kids got cut U15, the choir boy was cut U16, and what's left are tall guys with skills, people who double at cross, people who also do track, and then a keeper.
what i noticed as i progressed was as speed of play increased it would be like you would think you had a bunch of space and it would close so fast. and if you're not up to that, you're bench or gone.
so i think it's deceptive that it seems open to anyone. if you aren't fast, highly skilled, tall, aerial ability, good GK, the older you get the less useful you are. but because it's a popular sport they can pick from high volume.
that and there might be several layers of pro from well compensated to semi-pro stuff. multiple select and college teammates played some level, and i was offered a tryout but in grad school and turned it down.