Raw numbers of 4* and 5* players by offensive position not counting "athletes" who usually end up at WR, RB, or DB.
QB- 26
RB- 36
FB-3
WR- 47
TE- 15
OL- 49
Number of Rivals 4* and 5* ratios vs positions filled (one QB, one RB, 2 WR's, one TE, one FB, and 5 OL's).
QB- 26:1 = 26
RB- 36:1 = 36
FB- 3:1 = 3
WR- 47:2 = 23.5
TE- 15:1 = 15
OL- 49:5 = 9.9
IOW's, if you are HS TE you are more likely to be a 4* or 5* player than if you are an OL. Only the lowly FB has a lower chance. A RB has almost 400% better odds of being highly rated. A WR has more than double the chance while a QB has almost 3 times better odds.
Coupled with these facts, the recruiting svcs have the most difficulty predicting success for OL's and DT's. Almost none of those recruits will come into college ready to play like they are. There are huge physical transformations for these guys. Some who look almost ready out of HS may have just about tapped out their potential while some run of the mill 2* or 3* kid develops into a monster after being on a training table and S&C program for a year or two.
In short, NO, there aren't plenty of 4* and 5* OL's in any given class. And even if there were, you could easily sign 4 or 5 four star players and end up with a worse OL than if you'd signed all 3* guys.
Thankfully, I doubt Dooley is hung up on the subjective rankings Rivals and Scout put out on linemen.