Narratively speaking, this is Malick at his most tedious and sluggish, and I think the main reason has to do with the balance of main characters. Knight of Cups isn't great, but it at least had Christian Bale front and center; this has four, and the results are messy.
Where I at least prefer Song to Song over To the Wonder is simply in the world it depicts. As a musician, the backdrop is just something I can find an interest in, and I can't get over the idea of watching a Malick film that features members of the Red Hot Chili Peppers wrestling.
I wrote back in 2017 that Song to Song feels like a visual adaptation of Del Shannon's 1961 hit song "Runaway", which is featured in the film. I stand by that.