Personally, I don't think it's the prices. I think some people look at the price as the reason why they might not be interested, but hockey on average has the wealthiest fan base in all of major pro sports. So of any league, the NHL should be theoretically the safest to price elasticity.
I just think it's the world we're living in. Competition for your entertainment dollar is fiercer than ever before. Generations growing up seem less and less interested in traditional sports but instead are gravitating towards e-sports.
You've got to contend with the Netflix generation where sitting on your couch, watching TV and food delivery can be done with virtually zero effort whereas in contrast, paying hundreds of dollars to get up, get ready, drive through traffic, line up for security, food and beer, then having to line up to exit, drive through the same traffic to get home and then unwind. I mean, that's a lot of effort to watch the exact same game you could at home while not having nearly the same type of choices and options.
Personally, I could see this trend continuing for all traditional sports. I don't think anyone is immune.