I wonder if how niche music tastes have become has something to do with it.

Probably; it feels like less that 'young people aren't excited by bands" and more like 'to be a band that takes off the way they used to, you gotta be doin something different'. I don't think anyone's exactly clamoring for bands to do the same shit as your average Seether, Incubus, or Three Days Grace expies. Meanwhile, you've got acts like Polyphia, Zeal and Ardor, and Ghost running around out here doing actively different shit and seeing payoff on it.