Let's Start is a simple sing along song, although it's among one of my favorites, as far as I can see, it hasn't registered really at all with Haley's core fans...it does seem popular to sing the chorus along w/ Haley at her shows though.
I just think it's a matter of timing though. R&B and Hip Hop have dominated the charts for decades now, outlasting many previous genres before it, hair bands, new wave, grunge. I keep expecting it to start trending down, but I think it's morphed into a synergy w/ dance/edm music, that has added to it's longevity.
I think that's where Haley's talent for versatility might end up being a defining attribute that will take her up another level. Who knows what or when the next genre will be, someone with Haley's versatility and collaborative intuition might end up putting her into the next 'wave'