I understand but am reserving judgment. I 100% agree with you if the regression for the draft classes doesn't make them/their speed at par with stock roster players in 2-4 seasons.
Your worry about super freak rookies is valid. From what I've seen it depends on the leagues out there. Some have conservative stat padding rules so rookies won't have the XP to do damage. I've seen others where the top 10 qbs have 6500+ yards each. Those WRs are like pigskin terminators.
Garbage in, garbage out. If the league is sim, so shall be the players. The league I referenced above played sim, but the stats read NFL BLITZ. I wasn't shocked when half of the user teams had 10 or more 99 ovr players.