I'm not convinced DSB is not known to a younger audience certainly in the UK. She currently has 1,012,253 monthly listeners on Spotify which I think is unlikely to be mostly the aged or infirm.
Similarly, many of her videos on Youtube have many millions of views (Get The Party Started (8 Million), Goldfinger (2011 performance 6.9 million) with similar viewing figures for My Way, History Repeating & This Is My Life.
Her 2020 Album "I Owe It All To You" peaked at number 5 in the UK chart, her highest placing for a non compilation album since the "Something" album in 1970.
Still very much a current artist despite withdrawing from touring many years ago.