Georgia and Florida have a better recruiting area, I won't argue against that. But the point here is that Tennessee recruiting over the last two decades has been able to get equivalent talent to those two programs; in part by owning their own state.
Georgia only suffers minimal loses to Georgia Tech. But Florida does feel the pinch in years where Miami and Florida State have great years (with the exception of this year's anomaly by FSU). I think Florida is going to have a couple years of uphill sledding, at least from their typical standards.
But to say that Tennessee doesn't have a fantastic recruiting region of almost 7 million people that love and play football all year long is just ludicrous. Like you said, compared to Nebraska, they are the land of recruiting riches...
Again, it's relative. Based on recruiting rankings, Tennessee recruits better than Nebraska, but I would say it's easier to win at Nebraska. Why?
Tennessee typically ranks 3rd in the SEC East in recruiting and 6th overall in the SEC. Plus, Tennessee plays Alabama every year. So, they are playing 2 schools in their division every year that recruit better than them and at least 1 school in the other division that recruits better than them. Based on recruiting rankings, they play at least 3 and up to 5 schools in the SEC every year that have better recruiting rankings. That is hard.
In contrast, Nebraska typically ranks 1st in the Big 10 West recruiting and 4th in the Big 10 overall. Based on recruiting rankings, they would not play a team in the Big 10 West with higher recruiting rankings and they would play 0 to 2 teams per year with higher recruiting rankings in the Big 10 each year. That's pretty good.
Thus, I think it is easier for Nebraska to win the Big 10 West than Tennessee to win the SEC East. Scott Frost now has recruiting ties in California from his Oregon days and Florida. I think he would be able to improve Nebraska recruiting.
If Frost is looking for the better opportunity to win, I think he would chose Nebraska over Tennessee.