I think they're a great format to buy, but nowadays not that great to use. They offer the best audio quality of all physical media (fight me, vinyl enthusiasts), are really easy to handle (on par with cassettes), offers track selection (later cassette decks could detect silence but this doesn't work for gapless tracks), the equipment is rather cheap nowadays, it's a digital format without DRM... red book CD might be the best consumer media industry has ever created, my only gripe in the modern world is that its sampling rate is a bit off today's 48kHz.

However, I only rip the CDs to lossless and then rarely take them out of my cupboard anymore, don't even have a CD player. Using CDs in a mobile setting is a whole different beast, it requires a buffer and can also damage the discs in the worst case. But at home, pressed CDs live very long without any degradation in sounds quality, regardless of use. And ironically, buying them is often cheaper than buying non-physical only, though it often means that you end up with tracks you don't want. But that's an issue all physical media has.