Totally agree with this, fwiw. At least on the boys' side, it doesn't seem like there's much differentiation at all, and there are not enough truly advanced players to really support much above just the normal SoCal flights.
Case in point: when my son's club became eligible for NPL, the top 2011 boys team became NPL, and the F2 team moved up to F1. There was no perceptible change in skill level for either team; they just "shifted up" because that's how all the teams were shifting at that age. They could have just as easily stayed F1/F2 without introducing NPL, and achieved the same level of competition for both teams in the league; the whole introduction of the NPL tier seemed like just something to make parents feel better about their kids' progress.
Above list is missing EA/EA2 (and probably others). Many EA teams are strictly worse than SoCal F1 teams. ECRL teams are roughly on par with SoCal F1, in my experience. ECNL seems above NPL on average, but there's some non-trivial overlap in skill there. Almost all these leagues are just there for people to feel better about paying more money for club; there's only so much skill on the bell curve of player development.
Also, fwiw: Some of the stronger teams in SoCal F1+ (and beyond) are AYSO United, at least for my son's age group (2011). They seem to be developing just fine.