My father was a Peter Paul and Mary superfan. I don't care how old you are, I've almost certainly listened to more Peter Paul and Mary than anyone on this thread combined. It's funny, because he's an arch conservative, but he loved that hippie folk music, but PPM was his absolute favorite. It was on in the house hours and hours every week.
Multiple things can be true...
- They were without a doubt somewhat of a construct folk outfit, and not particularly authentic in the through line of Guthrie/Seeger/Dylan. Always considered a bit suspect by the folk dweebs who got mad at Dylan for plugging in. They were a somewhat artificial creation, emblemized by there is no "Paul", Noah Stooky adopted that moniker for the catchy band name
- Their talent and effectiveness as a trio is undeniable. From their voices to their arrangements to their stage camaraderie to their selection of what to play, they made a phenomenal amount of really, really good music.
- Their voices and harmonies and arrangements made them massively more commercial and more widespread appeal than most more "authentic" folk artists, not unlike the Kingston Trio in the 50s. These bands brought the folk ethos, including folk protest songs, to a much wider audience than the "authentic" acts.
- There was absolutely nothing in that era that frowned on "covers", in fact it was almost frowned on NOT to. And if anything, it was even more traditional in Folk music to play the compositions of others. Dylan's first album only had two of his own compositions. His ensuing work focusing mostly on his own compositions was a departure from the norm, and one of the reasons he often bristled at being pigeon holed into the folk niche.
- That said, some of their own compositions, some hits and some not, are great songs. It's not like they didn't have the ability to write and arrange their own music
- They were exceedingly, relentlessly commercial, for decades and decades, in a way that just isn't really in form with traditional folk artists
- Peter Yarrow was a pedophile, was pardoned by Jimmy Carter, and pretty much just had it swept under the rug over the course of years and years of PBS specials, childrens albums, etc.