Two reasons. First, Tennessee depends on other talent-rich programs being on down cycles more; I seriously doubt that will occur with the degree it took place in the 80's and 90's. Second, Fulmer was a very rare recruiter; no other coach has shown a 10+ year ability to land top-5 recruiting classes an average of once every three years or more.
What changed? First, ESPN revolutionized college football. Every program has serious cash, and with that cash, we have professionalized coaches who are highly unlikely to let their programs slip continually. Second, the SEC integrated, which is what made the pre-1975 comparisons to college football mostly irrelevant.
If you want to see additional examples, look at the non-talent rich programs across the country and their inability to compete at a top-10 level since the early part of the 2000's. Nebraska, the program most like us in combining great tradition with limited local talent, has tried three different style coaches, and none has returned them anywhere close to their glory days.
My take on Fulmer was not that he would return us to the 90's status; it was that his 2000 teams were still over-performing compared to what his likely replacements would perform. Fulmer didn't change; the circumstances changed, but his unusual recruiting ability kept us above where we would be without him. Now we get to see in live color what a Fulmer-less Tennessee team really looks like.
