I think advanced scouting should have some sort of effect on either viewing current ratings of other players in the league (not on your team) or tied in somehow to scouting.
In real life, an "advance scout" is somebody who, for the most part, scouts other teams in the leagues to get an idea of their strengths and weaknesses. It kind of makes no sense that I can put 0 in my advanced scouting and still get a perfect judgement of the current skill level of every player in the league.
The above suggestions are too radical of a change, however. At this point, you can't just turn off the lights on current ratings. It would have to be a much more subtle change.
My suggestion would be to add much more variance in the player's development curve, but specifically the LENGTH of that curve. I think this would mirror real life better and also make advanced scouting more valuable.
For example, look at Johan Santana. He signed as a 16 y/o IFA and was obviously talented but had tons of control problems. However, his control kept improving and it wasn't until his 8th professional year (when he was 24) that he finally walked fewer than 3 batters per 9. Jayson Werth is another example, he is just hitting his peak at 31, and has steadily improved ISO, walk rates and his platoon split has evened out.
On the flip side, you have a guy like Felix Hernandez who, in just his 3rd pro season at 19 was basically as good (or better) as he is now. Ditto for a guy like Ryan Zimmerman who was drafted in 2005 and hit the ground running in the majors, but had 3 straight years of basically being the same player. Of course, he did have an uptick in power last season, so maybe that will continue, but that's just an example off the top of my head.
The point is that, in real life, players have very different growth curves. Some have great potential with one or two glaring weaknesses that either never improve (keeping them mediocre) or improve greatly and make them a star- like Johan. Some, like Jayson Werth are fairly unremarkable but gradually improve all facets of their game until they are excellent players.
Some are ML-ready very early but never hit superstardom. Some are ML-ready very early and get even better. Some players develop power first and batting eye later. Some don't add power until they fill out in their late 20s.
I think that would make the game a lot more interesting and realistic and also had a huge element of strategy with regards to advanced scouting. It could also be phased in slowly enough so as to not totally shake the whole game up in one or two seasons.