Instead of desirable food we end up with drought resistant brush of one type or another. Ceanothus, manzanita, etc.
Both of those are genus names that are commonly used as catch-all names. Ceanothus has more than 50 species and manzanita a lot more than that. It takes a botonist to sort them out. We have a lot of ceanothus in southern Idaho but it's usually just called chaparral, which it isn't really.
The thing that's really screwed up the ecology in much of the west is cheat grass. It spreads and grows thick between the sagebrush. It matures and drops its seed early in the summer then the stems dry out. If a fire gets going, the cheat burns extra hot which kills the sage and other native plants. All that's left if the cheat grass seeds which come back with a vengeance the next spring. With the sage gone, the cheat is all that survives. Without cheat, the sage will survive many of the fires but with the cheat, the fire clears the land completely except for the cheat seeds lying in the soil.