The era ended in 2009 when Jay Leno had to retire for the first time. Letterman lasted until 2015 but he was not the same at the end because he was becoming political.
Today I can watch Mr. Beast on streaming. No need for me to watch a "Late Nite" program on TV.
And Carson himself has been back on the broadcast airwaves for a few years now weeknights at 11 PM on the AntennaTV network. Dated material and all, it is still better than this current stuff.