Rock bands might be OP, they might be worthless, they might be so RNG-dependent that every different rock band is either OP or worthless... But none of that really matters.
The bigger picture here is that the culture victory is starting to look better than ever before. It won't come to fruition in this cycle, because the Civ 6 culture victory started off way too deep into the BNW system, but we're getting somewhere.
Going forward, the devs seem to be figuring out that the current conception of great writers and musicians is bad. Music and literature should not exist as individual "great works" which can be moved from city to city, or sold to another civilisation. It's a cool way of handling artworks and artefacts, and the museum/wonder theming minigame is a great addition to cultural gameplay... But it's completely antithetical to how music and literature actually work.
So, writers and musicians are bad (conceptually speaking, not in terms of power/usefulness). And unless Firaxis can get the rights to dozens of the biggest hit singles of the past 100 years, great musicians are always going to be bad. Because of copyright restrictions, 20th and 21st century music needs to be implemented in the abstract. No named artists, albums or songs. The rock band is a big step in the right direction. Even if it is a hopelessly Baby Boomer concept of how modern music works, and really only captures the spirit of a few genres which were in vogue between around 1967 and 1990... But what else are they gonna do? Add rappers, DJs, popstars, orchestras and singer-songwriters as different units? In game terms, they'd all do exactly the same thing. Maybe use a more generic term like "recording artist," and have a bunch of different unit models in different game eras.
The next step (probably in Civ 7 at this point) should be getting rid of great works of music entirely. Composers should be abstracted, represented by the culture generated in Theatre Squares (or by specialists). "Musical units" should first appear in the Industrial or Modern era, when orchestras, opera troupes and jazz ensembles start touring using the same mechanics as the rock band.
I'd keep writers, but works of literature shouldn't be physically present in a building on the map, and they definitely shouldn't be able to be "traded" to other leaders. Who can forget when England traded the Canterbury Tales to Spain in exchange for a shipment of amber and horses? Great literature should be "collected" over the course of the game and displayed on its own UI panel. Its culture should fluctuate depending on how your empire is doing. In a Dark Age, people are printing fewer books. Once you develop electricity, your literature gets a culture boost as you start filming adaptations of the classic texts. Stuff like that.
I'm a little off-topic here, but I'm genuinely delighted that the devs are starting to think about more accurate ways to represent the cultural role of music and literature in-game. It's goofy, but if anything it's way more realistic than generating tourism by popping the world's only copy of Beethoven's 3rd symphony into a single broadcast tower to play on repeat for eternity.