I moved your post to Lightroom, from the Lightroom Classic.
I can't read the error message, so I am not exactly sure what it says. You should be able to delete photos from Lightroom, but you can't actually delete the catalog. The catalog is part of your Creative Cloud subscription. It can be empty of photos, but Lightroom will still be there as long as your account is active.
Well it's not an error message it's just a confirmation modal panel that tells me to write a specific message to be able to click on "Delete". But even if I type the exact message, the delete button is not available and therefore I can't delete my photos.