Your line of thinking is exactly why Alex Davis is a starter, and what the coaches are thinking. So you are in good company and quite honestly not wrong right now. Domann and Ferguson could work against spread teams, but against Wisconsin and Iowa who we have to beat to win the West, probably not a good bet. They are designing packages to get Domann on the field more.
With that said, let's look at snaps on the field last year, tackles, and sacks:
Luke Gifford 806 snaps, 62 tackles, 5.5 sacks
Trying Ferguson 290 36 tackles, 1.0 sacks
Alex Davis 253 5 tackles, 0.0 sacks
JoJo Domann 183 snaps, 19 tackles, 1.0 sacks
Alex Davis has to turn a major corner, and when Ferguson and Domann are on the field, they make plays and make things happen. While Alex Davis isn't tackling anyone at all. People can improve, so hoping for the best, but this is certainly an area of concern.