There is tons of jazz out there on CD and streaming services. Some (but not all) of it requires stretching one’s tastes. That’s not easy to do in middle age and beyond -- but it can bring a lot of musical pleasure, and I think it’s got to help the brain stay younger.
But even without too much stretching, consider Ron Carter, the most recorded jazz bassist ever -- about 2300 recordings (including some with Miles) and still going strong at 85. A fabulous bassist, with a solid, beautiful tone and who plays just the notes that sound great and interesting, and nothing more. There is a PBS American Masters show about him, well worth watching. And if you want to hear his music, just look on any streaming service or YouTube or probably even Wikipedia to find albums to try. Among other things, I like his Chesky album with Rosa Passos.
For older (mostly dead) singers, consider adding Betty Carter, Carmen McRae, Abbey Lincoln, and Shirley Horn to your list. For newer (mostly living) singers, try Dave Tull, Champian Fulton, Cecile McLorin Salvant, Tierney Sutton.
If you really want to get adventurous and you have an uninterrupted hour to spend, listen to The Adornment of Time by Tyshawn Sorey and Marilyn Crispell, both incredible artists. I found the time and effort amply rewarded.
Jazz is not disappearing. It is progressing.