This article dispels the myth that radio is a dying/dead medium in the 21st century. What's interesting to note is the increase in the number of radio listeners who are under age 40 (18-34), the market segment that's most coveted by advertisers:
The problem is that the opinion depends on what your (plural) bias is. Radio is still very important. However, it isn't as important as it once was. That was also true 50 years ago. If you look at 2017 vs 1997, radio's importance is down. If you look at 1957 vs 1937 it was down then too. Statistics can be twisted to fit whatever your agenda is. I have a problem with the "reaches" methodology. The fact that I turned on a terrestrial station for a minute this week counts as me being reached even though the contact was meaningless.
Bottom line, radio is still very important and will be for the foreseeable future. It will never be as important as it used to be and nothing is going to change that.