Two "folk-singers", one American and one Canadian, come to mind. Kate Wolf from California died an early death from cancer (I believe). She is worshiped by many and panned by a few. Personally, I feel she wrote at least one classic , "Give Yourself to Love". I have a few albums and they are uneven in the quality of her songwriting. She probably had more good ones in her future if she had not died young.
Then there is Stan Rogers who died in a plane accident (not a crash). Obviously, he was in the top of his form when he died. I haven not heard a bad word about Stan. A few people believe he was over-rated. He had a wonderful voice, a love of his country and its history, and a pretty good way with words. I am sure he would have become more famous had he not died young.
Those who die young and aren't so good are probably just never heard from. Therefore, the young who die "bad" do so in relative obscurity and sink into oblivion.
Some old guys continue to do well. Doc Watson and Pete Seeger come to mind right away although both may be losing a step in their dotage!
Roger in Baltimore