104.5 is ran like a top 40 station, except it plays only what is topping the Alt Rock charts. I agree that 104.5 isn't really "alternative" at all, in fact it's as mainstream as it gets, but that is all subjective.
Alt rock, by today's standards, is more of an aesthetic rather than a definable musical style. Punk, grunge, shoegaze, britpop; all that stuff that made 80s-90s alt rock what it was are styles that have become very niche and underground today. The defining musical styles today that make up modern alt rock is electronic, rap and dance-rock.
What you're discussing would be considered classic alternative, which is a format sorely missing from most markets. A station that focuses in on 80s-early 2000s alt rock with bands like Weezer, Green Day, Oasis, Pixies, my bloody valentine, dead milkmen and so on.
But we have to remember that if this new alt rock music does genuinely connect with its listeners or audience, who am I to complain? I have spotify, so it's not like I depend on 104.5 for my fix of alt rock.