I'm not wading into the opinion of whether the DAYS score is good or bad. What IS relevant is that the show on a whole has not resonated with enough buyers across the board. No element of it has "hooked" enough people to buy at a sustainable price point. The story, subject matter, score, characters, and performances are all a part of that. Audiences are typically bad at articulating what they like and dislike about a show. It usually boils down to a "yay or nay" when recommending a show to someone else, and this show seems too dark, too sad, and too intelligent to illicit a "yay."
FUN HOME had tough subject matter but it was also an inherently warm, universal show about family. SWEENEY is a black comedy about murder and it wouldn't be as commercial-adjacent without the humor or its sweeping, melodic score (and yes I know the original did not recoup). Almost everyone dies in LES MIS, but it ends on a note of hope and a theme of love –– and, again, a melodic score. DAYS is a bleak show without the qualities that made those shows successful to mass audiences.