Perhaps we need to define how "important" is used as a descriptor. Certainly the word can be used within the realm of music, its development, originality, so on and so forth. The same can apply to individual songwriters and musicians. All within the framework of music. Innovators, virtuosos, classics, etc. Sure. There are surely important people, songs and compositions.
Using "important" as a descriptor when referring to any particular music or musical piece itself or to the musician / composer / singer as if its importance is somehow world-affecting on the macro level seems aggrandizing and silly to me.
I recall a few years ago that Guns and Roses had a new album or a tour that was kicking off and the promotional spot on TV delicately mentioned that it was "the most important" such and such of the last so many years. Important? Really? What makes those meatheads and their music so important? We're talking GnR here. Sure, you can really dig them, rock out to them and enjoy them. Important? Hardly.
Similarly, Brandi Carlile released The Joke and someone on Surly decreed the song to be "so important!" Certainly they can like the song. I agree it is thoughtful, well sung and arranged. Important? For someone? Sure. Just important because, "well it's important!" Nah.
It's just my opinion. I'm not looking to fight over it. You asked.
OK....let's fight.