They're still underrated. You don't often hear Noll's name being mentioned by pundits as one of the top coaches of all time. Yes, they do mention him but it almost seems like an afterthought. Walsh, Landry and Shula among the old timers tends to get the most pub and you even hear more about guys like Parcells or in current day Bill Billichick.
As for Bradshaw he's underrated among the QBs simply because he didn't put put the mind boggling numbers and the first half of those Steelers championship years it was more of a run oriented offense than anything else. He did get to the throw the ball more during the last couple SB runs though.