I'm not sure that Denver hasn't greatly imroved their secondary, for example, but they are picking up a lot of older players who might or might not still have what it takes. That's why you play the games.
You don't have to like Lombardi, but he has a lot of experience and watches the Broncos closely. Hence, a view from the other side, found here:
Does more mean better?
I don’t like the Broncos’ offseason so far. Don’t believe that all the new players are an improvement. Quality is more important than quantity in the UFA market. I think Andra Davis is one of the slowest linebackers in the NFL and feel that many of their additions are role players and not top-level talent. It seems the Broncos are behaving like a college team that recruits from junior colleges instead of hitting the high schools for long-range solutions. I might be wrong, but my evaluation of some of the players the Broncos signed is not in tune with Denver.