There is an attitude problem at the moment. But if you think the coach doesn't know that and that he doesn't see the other problems you are wrong. He can't just come in and start dropping people and changing key positions. Nearly the whole team would be dropped/changed. He needs time to fix the problems.
Fixing a wrong attitude/culture is difficult and you have to be careful. He knows about the 1, 5, 6, 7, 9 and all the others that are not performing. But unless the attitude is fixed nothing will change. If you bring in new players pretty soon they will adopt the same poor attitude. I know there's more to it than that and so does the coach. He knows things need to change. There has been four games played, we still have a while left in the season.
Let's be patient while the correct changes are made without disrupting the whole team and causing further problems. Do you think it's possible that if the coach makes so many changes the whole playing squad starts to lose faith in the coach. Maybe they start playing worse from the pressure of being dropped. I get it that changes need to be made, so does the coach.
He will make them carefully while trying to improve the attitude. Men, especially football players, are a sensitive bunch. And some of these "men" are still just kids. All the arguments for dropping them like "they get paid a bunch" , "they need to harden up", "they need to respect the Broncos Jersey" etc. are valid but other things need to be considered as well.