Early on in "Crazy Ex-Girlfriend", the show made it clear that the songs are in Rebecca's head, that she's not even that good at singing in real life. Nevertheless the songs are a delight. Even when things are hard, or sad, or everything in between. The "Sexy Getting Ready Song" was weird and strange, and I've told people over time that it took until "Face Your Fears" to see the vibe that the show was going for, but it was all there from the beginning. The songs are a sign that Rebecca doesn't see the world clearly, not because they are songs per se, but because the songs contain an awareness, both of realities Rebecca isn't ready to see, but also clues to the larger pop culture landscape.
"Crazy -Ex-Girlfriend" isn't blaming pop culture per se, but it is taking a look at the behavior that gets held up as romantic, at how these things look different when done by people of different genders or different sexualities. Whether it's the idea that a woman who truly wants love would of course mold and wax and pluck herself into a better, skinnier, hotter version of herself, that shipping people who have told you they can't make a relationship work, or that folks who are sarcastic and mean might actually need deep therapeutic work and possibly addiction counseling before they are ready for a relationship, and all sorts of things in between, "Crazy Ex-Girlfriend" has addressed both the deep dark scary stuff and the oh my gosh excitement of bonding with friends through song.
Certainly many of Rebecca's various coping mechanisms have been shown to be unhealthy, but the singing, real or imagined has helped this show seem wonderful and often bright as it addressed a range of things, many of them dark.
It's possible you could argue the songs are another mask, but I think the songs provide a useful balance. Musicals often go places that would be fairly unbearable in pure play form, whether it's failed revolutions or mental health struggles, or more successful revolutions. I always talk about telling someone I was seeing "Fun Home" and "Hamilton" the same week and they thought "Fun Home" sounded dark, and I was like, but you know lots of people, like lots more people die in "Hamilton" right? "Fun Home" had songs too, which is honestly part of why I added it to the list. (In fact it has a very sparkly song, and love song, and a longing song.)
So, the songs in "Crazy Ex-Girlfriend" helped keep the darkness away, even when the songs were about the darkness.