Based upon your apparent knowledge of SoCal, it seems as if you live here and or have spent a decent amount of time in SoCal. All I can tell you is that my interpretation of what I saw in So Cal is a well developed Latino soccer culture that is missing some developmental "infrastructure" pieces. It is surrounded by suburban areas of mixed Latino and other ethnicities with significant interest in soccer but still lacking numbers when it comes to kids just getting together to play soccer on a regular basis. In the outlying areas, we have a lot of kids playing club that play on weekends, practice Tuesday and Thursday but don't have friends with whom they can get together with on Monday or Wednesday or at lunch to kick a ball around, learn new tricks or what have you. This doesn't mean they can't get good but it means there are more barriers. They have to travel further for games, if they are going to practice extra it becomes a solo effort and is more like work than hanging out and having fun or they have to travel for their friendships. For me, the soccer culture is less about whether the kid plays on a team and more about what he chooses to do when given the choice. Do they bring a soccer ball or a volley ball to the picnic? If it is a Latino family from south central, it will likely be a soccer ball, if they are from east LA, it might be a football or basketball instead, some of my wife's cousins would definitely bring a soccer ball but the cousins from the other side of the family (been here longer..) would be more likely to bring a football or basketball. Compared that to the Mexican relatives in Mexico? no comparison. Your experience may be significantly different than mine.
It will be interesting to see if this league will change their scheduling format. I think currently they meet at neutral locations for 3 days and play like mini tournaments. This will be much more expensive for the migrating DA teams.
I spent a year in England back in the 70's when I was in 4th grade. Had never played soccer but of course they did at lunch and gym. At first I was the last kid chosen but at home I had nothing to do (not even a TV until the last month or so) so I would kick a ball around in the back yard while pretending winning shots etc. After six months I was the 4-6 player chosen and was getting better quickly. No hanging out with friends, no playing at a park etc, just by myself at home and at school for small bits most days. Moved back home, no one played and lost it. Just saying skill can be learned and forgotten quickly at a young age and can be done mostly solo.
Where I live in SoCal there are probably more competitive soccer players than basketball, football and baseball combined and a lot of soccer balls at picnics. But the numbers of picnics are down, numbers of kids at picnics are down and phones might be more popular than any sport.
Not saying skill can't be learned alone. I do believe it is more difficult to do for various reasons even before the self discipline is factored into the equation. You, as a kid, had a serious motivator...fitting in is extremely important to young kids. In the US, it sounds like, you lost that motivation because the soccer culture was lacking and you no longer had any real motivation to be good at something nobody else cared for.
If AYSO is included, than it isn't even close. Football and baseball have really lost their share of the market in the past 50 years. It doesn't seem to hurt football too much at the high school level and above because it is still the money sport at hs and I think also because it is far more dependent upon athletic abilities and aptitudes than it is on skills that must be honed over years and years of dedicated practice. I would say that whereI live in SoCal I would say there are probably more completitive soccer players than other sports as well, but things do change some once hs begins. The main sport that has significant league numbers would be basketball. I don't know how the club soccer numbers compare to the basketball numbers (or the elite travelling basketball teams vs the elite academy soccer teams). My guess is that the basketball numbers are less but I really don't know one way or the other. I would say that there are far more pickup basketball games going on regularly at all of the playgrounds. In my area, there are groups of 4-10ish that you occasionally see playing soccer. You also occasionally see a parent or a paid coach training a kid but these things, while far more frequent than even 5 years ago are still not particularly frequent.
But it has hurt it. A bunch of kids start off in soccer and love it but switch when HS teams don't have teams or they think there's no money in it. If the money side ever starts getting decent or close a lot of those kids will stay with it.
This isn’t a knock on ECNL because I have little experience with it outside of our local club, just some observations and a question. One of the things I liked about the DA was the high quality training (only can reference my sons team/coach) that was over 10 months. I kept an eye on our club’s ECNL team and it seemed a bit disjointed. They had kickarounds in the summer and then the 9th graders went to play high school while the 8 graders played in a local league (almost rec level). Then in late October they got back together and trained for a week or two before they went to the first ECNL event in Vegas. The team did mediocre. After the event they trained off and on over the winter and then started league games in February. I have been asking our club if ECNL (or at least our program) will follow the 10 month model for kids that don’t want to play high school. It is strange to me because apparently some teams are on the opposite schedule so they arrive to the showcase in form while a club like ours is effectively in preseason. Do clubs like Crossfire and Pateadores that had strong DA programs continue year around or will they shift to the split season that ECNL seems to have?