I concur with this and wish I had made the same point.
My reason for bumping up the ratings for prospects is primarily so teams will play them (or improving dev traits so they'll progress a bit quicker despite not playing). They might progress to be too good down the road, but I'm at the point in this franchise where I don't mind experimenting.
My QB is a generated prospect who is ranked I think 92 overall. He was a 74 or so as a rookie, sat one season, then steadily progressed. Similar prospects on other teams stall out about 10 points worse in overall. My running back was a 99 for years and is now mid-80s as he nears retirement. He was a 63 overall star dev rookie who blew up quickly. That never happens with CPU teams because they won't put a 63 overall in the lineup.
That said, the Bears have had one of the leading passers in the NFL for most of my franchise. Anthony Gordon from WSU, who I originally drafted late in my first draft and ended up trading. I don't think he ever got above an 84 despite starting with a star dev, earning an x-factor, and playing regularly and playing well. He might've finally started to get PT when he was too old to progress quickly, but still ... Aaron Rodgers never started a game until he was 25, so quarterbacks who sit on the bench for a few years then break out should still have the ability to earn elite attributes.
My next experiment with this franchise will be taking over as coach/owner for several teams and setting depth charts. I'm not sure if I can toggle autopilot on without having the CPU redo depth charts, though, which would be unfortunate. If I can't get teams to play young players that way, I'll likely just end up building rosters bereft of experienced players so they have no choice. I don't think we can set up training/upgrades/scouting to automatic for individual teams—I recall it being a league-wide setting—which would help automate the parts I don't want to waste time on while retaining some roster control.
Overall, though, I do gotta say I appreciate that franchise provides the options to make these adjustments well into the start of a franchise. One of the things that annoys me most about The Show is that once you start, you can't add/drop user-controlled teams. Not that manually fixing issues replaces quality game design, but I'm glad that at least if EA won't devote the time into making things function perfectly, it's willing to give us some control to find workarounds we can live with.