The return of the 80s is, or rather was, just a current trend. Next up will be the 90s/00s, which can already be seen in make up and fashion, and I'm sure media will follow soon as well.
Wrt/ Hollywood: I think they are not the monopoly they used to be, because the powers are shifting by streaming, and short video services. Similar to how AAA games are more stagnant than the indie gaming scene.
"Music" is too broad to "get worse". There are trends in music that can be considered bad, such as the lessening dynamic range of the recordings - the Loudness War[0]. But there is more music than ever, computerized or not, so if you find that some source of music is bad, you just need to look elsewhere. Music production is easier than ever, so even very niche sounds are kept alive, like the lofi sound of post-punk decades ago[1].