>> Advanced affects accuracy of current ratings for All players of all ages. It's instantly valuable. <<
Not true. Everybody seems the same, accurate current rating.
ADV budget determines the accuracy of the projected ratings you see.
Except for major injuries & DITR, development follows a predicable pattern. If you can see 2 seasons worth of ratings, you can come within a few points of knowing exactly how a player's ratings will end up. Especially on your own team, where you can control playing time and, to a degree, MinL coaching.
It seems that development can be screwed up. It also seems that once you cover the basics (playing time & acceptable coaching), players are all going to develop on almost exactly the same pattern.
Which is why you see a lot of long-term successful owners with 0 or very low ADV. It's not that ADV doesn't do anything. More like there seem to be better ways to invest the money.