1) It remains to be seen if any of the artists you named stand the test of time the same way artists like The Beatles or even the Piano Man did. Sure, maybe right now you can't go 10 minutes without hearing Chainsmokers on the radio but I really don't believe they'll be played on oldies radio 40 years from now.

2) Unless it's a room full of old hardcore music enthusiasts, yes, that's exactly what they want to hear. Don't fool yourself into thinking that most people are into hearing stuff that's off the beaten track, deep tracks and B-sides, etc. Most people want to hear a familiar song that they can hum along to (son can you play me a memory/I'm not really sure how it goes/but it's sad and it's sweet and I knew it complete/when I wore a younger man's clothes).

3) I'm guessing, simply by virtue of being on reddit, that "our demographic" is early-20s, similar to my own age. Tell me honestly that you don't get a big smile on your face and rock out if you're out somewhere and happen to hear some Sugar Ray or Blink 182. We all have a soft spot in our hearts for music from our youth, that doesn't change. I sure as hell hope that when I'm in a nursing home 60 years from now and they hire a band to come play for us that I'll be hearing All Star and What's My Age Again? (okay, maybe not that Blink song specifically but you get the point).

Unless you are an established enough artist to have your own catalog and to be able to use your own name/material as a draw, you can't stray too far from the stuff that people know, or else you're going to lose them.