but there is a lot more than that.
Part of it is Bronco's recruiting style, philosophy and errors, part of it is just how exclusive BYU has become and so the general LDS population doesn't hold as strong a tie to the university as it once did, the closing of the Ricks / BYU-H sports programs also has cut down on the breadth and extent of LDS influences in sports, the rise of Utah's program, the societal and church attitudes that have resulted in higher percentages of boys (and girls and adults) "falling away" from the mainstream church, I am sure I could make the list much longer, but the end result is that, BYU hasn't been landing very many of the top recruits.
The age changes in missions is one area where I do think there will actually be positive recruiting gains for BYU, we shall see if it actually helps with some top recruits in the near future, as it hasn't really had that effect so far.