Among P5 programs

61% of 5* are drafted
23% of 4*
5.1% of 3*
0.5% of 2* or unrated

So a 4 star is about 4.5x more likely to be drafted than a 3 star. And a 3 star is 10x more likely than an unrated guy.

That's looking at the player, but let's look at the teams. The team with the better rated recruits wins 73% of the time. Not a guarantee by any stretch but a pretty solid indicator that incoming talent matters.

Data from https://lastwordonsports.com/collegefootball/2021/07/12/what-do-those-star-ratings-mean/amp/

Now let's look at BYU from 2008-2017 (chose those years because by 2018 so many of the players don't have their ultimate fate decided.  That means I didn't include Wilson (3*), Milne (2*) or Allgeier (2* and not yet drafted) but also didn't include a lot of guys who won't be drafted.

N/A% (0/0) of BYU 5* are drafted
23.1% (3/13) of 4* (Kyle Van Noy, Fred Warner, Bronson Kaufusi)
1.4% (2/138) of 3* (Jamaal Williams, Sione Takitaki), and
4.2% (3/65) of 2* or unrated (Brady Christensen, Chris Wilcox, Khyris Tonga)

So looks like we do very well with our 2* recruits, especially compared to the national averages, especially since Sitake has come in.  But we've also been pretty comparatively terrible with our 3* recruits getting to the NFL.  And our 4* recruits get drafted at almost exactly the nationwide expectation.

Overall, 2.4% of our 3-star and below guys get drafted.  And 23.1% of those above 3-star get drafted.  

Given that (and I can't believe I have to say this), if going to the Big 12 allows us to replace a lot of our 2* recruits with 4* recruits, we will almost certainly be a better football team.