"2nd 2020 team has 10 former blue players. What happened , did they
just become average players" ....

Hello? ..... when the kids start out... there are 1, maybe two teams in the youngest age bracket. Those kids ALL make it regardless of skill... no don't get me wrong some of those girls are good... and some will remain at the "top" ... each year more and more parents drink the juice and bring their kid out to tryout regardless of their skill ... the MORE kids at tryouts ... the more competition ... you seeing the picture now... your super star is no longer a super star relative to the other kids that may now be coming out ... but waited a year or two to do so.
By their 4th year there will be 5 or 6 teams ... Example: the 2019 bracket.
The cream always rises to the top... the middle layer is interchangeable and some float to the top and then back down to 2... the bottom players on each team will keep getting pushed down, how far down will depend on the number of girls that come to tryouts and how many teams they make. FAF of the Daddy coaches and politics as well as home town affiliations of the coaches/personal agendas will ALWAYS PLAY A ROLL... I doubt there is any diamond in the rough in the 3rd, 4th, 5th or 6th teams. The organization knows who is coming to the tryout. If they are a stud, they will be placed accordingly and someone will be displaced by the new talent. This is Shark tank in real life. If you can't deal with it don't waste your money.