CDs are great.
CDs are a cheap way to store high-quality audio.
CDs are an established technology. Other similar technologies are either older and inferior (such as cassette tapes), or more complex and cumbersome (such as BD-A, which bakes in DRM). Because of this, and do to its age, equipment that supports CDs is inexpensive, both new and used.
Because CDs have largely been supplanted by newer technologies (primarily digital media distribution), obtaining them (both empty and with music) on the used market is cheap. Typically I go to thrift stores and browse the CD section looking for new (to me) music that intrigues me and that I want to listen to.
However, I don't use CDs.
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That's technically wrong. I do use CDs. I sometimes burn disk images onto CDs to use on computers that can't boot from flash drives. I rip CDs that I get to add them to my (legally obtained) music collection. I just don't use CDs to play music.
CDs are an inferior way to play audio in our current society. They require specialised hardware (that isn't a general-purpose computer). There are only three CD players I have access to: a car player and two stereos. The car player is obviously inconvenient, and both stereos are inconsistent. In comparison, I have ~15 computers/phones that support playing music. This is admittedly biased, but for a more average perspective, many cars no longer ship with a CD drive, while an extremely significant portion of general-purpose computing devices (computers, phones, tables, televisions) are able to play music from files, all while being much more accessible than even a portable CD player.
Playing CDs damages them. Handling CDs damages them. In comparison, digital storage (especially well backed-up storage) can last longer, without losing quality while it degrades
Dedicated music playing hardware is much more integrated. I can carry my entire music collection on a dedicated music player, or even a flash drive, with room to spare. This is much more convenient than lugging around ~100 CD cases, or even raw CDs in a book (please don't), and taking them out whenever I want to play them.
These downsides make it incredibly inconvenient to play CDs. However, I still appreciate their price and high-quality audio. Since high-quality audio storage formats (namely FLAC) exist, I deal with this by ripping my CDs into FLAC files. I can then play these FLACs wherever I want without the hassle of a physical CD. This seems to be what a lot of music people do: rip CDs they obtain, then listen to the resulting files and not the CD.
I like CDs, but I never use them.
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Some details about my setup:
I use the fre:ac program to rip my CDs. How I typically do this is obtain a lot of CDs over a period of time, then I bulk-rip all of them in a single sitting.
My current music player is mpv. I use it through the terminal, passing the folder (each folder is the result of one CD) as an argument. Every other music player was too complicated for me; they all had unnecessary features, were too bulky, and were slow to launch. All I want in a music player is a way to select an album (i.e. CD), ideally at random, and play it, while showing me how far I've played a track.