You're clearly not looking hard enough. There is so much new music available. In my opinion we're in a sort of golden age of music. It is trivial for artists to publish new music and it's even easier for consumers to get it.

Discoverability remains a problem but even still, it's a lot easier to find new stuff than it was just 10 years ago. You still have to do some work if you want to find new examples in genres you like.

Arena filling artists are not all that different now than they were at any other time. It's pop music to one degree or another. The genres that are more popular get the bigger venus. AC/DC style hard rock enjoyed a run in the 80s but is currently 'out' but that does not mean it's dead or will die but the next Iron Maiden won't be shoveled to you via top 40 radio, you'll have to discover them and i guarantee you they're out there.