Off the top of my head, LSU probably signs less than 50% 3 star guys, though I would have to check that. I imagine the 4 and 5 stars make up over 50% of the signatures. So it's a smaller group to begin with and sure, some of them do little, but a fair number of them have been major contributors, if not outright stars. The percentage may be higher of ones who don't do much than ones who play like they deserved more stars, but that just goes to my point that I don't care about stars. You can either play at an elite level or you can't.
I don't know how it goes at most schools, but at LSU the number of 5 stars who wound up with 2 star careers is surprisingly long. Not all of them of course.....you have your Patrick Petersons and Leonard Fournettes, but man, for every one of those there's at least one more that's like "Oh yeah....I forgot about him....we had high expectations and then never heard from him again."
The majority of the revolving door of LSU greats who go on to NFL careers has come from the 4 star ranks. Guys that you would think would've been no-brainers for 5 stars, but weren't.