I assume you are referring to a physical copy of the Sega CD. As long as you still own a Sega CD you can play physical copies of games. Recently PlayStation closed down their online service for PS3 so you cannot access any digital games you may own even if you still have a PS3.
Or the service is no longer supported. I remember buying some PS3 games digitally but can’t access them on my PS5. Load of BS.
I can’t play my Sega CD games on my PS5 either; difference is that I’m not complaining.
I assume you are referring to a physical copy of the Sega CD. As long as you still own a Sega CD you can play physical copies of games. Recently PlayStation closed down their online service for PS3 so you cannot access any digital games you may own even if you still have a PS3.
And there’s no other way to play those games. They’re pretty much gone forever alongside the money spent to purchase them.