Westerns were largely replaced by cop shows such as HAwaii 5O.
'The Simpsons' had an episode featuring Dennis Weaver in which that fact was explored, Bart tries to bring Westerns back into popular culture. It was really funny, called 'The Lastest Gun in the West'. I recommend it if you can find it.
A modern western series is Yellowstone with Kevin Costner, I haven't seen but intend to get round to it eventually.