Overall we were a run first, pass short team last year. We had only a handful of completed long passes. Teams defended us that way with Georgia and Miami FL being the most effective. No matter what happens in Spring ball we will, until we demonstrate a long passing game (and hopefully will) teams try to make us one dimensional while focusing on stopping our short passing game.
Agree with your comment in that while St Brown was our leading receiver his total number of catches and yards doesn't look much like a game breaker. With Kizer there for his SR year he would have had far better stats more reflective of his speed and athleticism.
The biggest issue to be solved is how to get the ball deep and hit receivers in stride. Last year BW didn't do that in the early games and we stopped running those patterns as the season went on. Think part of the issue was play calling: inexperience = simple reads to avoid turnovers resulting in almost all passes being less than 20 yards. When early results on long passes were not good the focus was on what worked.
Given the issues at RB (we can't afford to run too much as we not only have to avoid injuries but also don't want them beaten up by seasons end) we need to have a "normal" passing game that will keep us two dimensional vs anyone. For BW to lead that think we need to see both better and faster recognition and mechanics that give us a long passing game. Hope that happens.