We have recruited LDS kids very well since Pope took over.
Hall, Saunders, Wahlin, Collin Chandler, etc.
Hall and Saunders are going to be starters some day.
The lack of Junior/Senior LDS starters is due to the fact that Pope didn't think the Rose recruits were good enough to keep in the program. Also worth noting that there has been a slight drop in LDS high end talent in recent years as you alluded to.
BYU won't be able to fill out every position with LDS kids. They will fill in the holes with the portal. I don't think BYUs problems this season are lack of "bigs". IMO the problems have been related to poor guard play.