"Rather, it's just my usual dislike of any singing that tries to sound like someone else." Well, folk musicians routinely tried to sing like other human beings who were folk musicians. E.g. Stick McGhee was likely trying to sing "Railroad Bill" like his father, and since I don't have any recordings of singer-guitarist George McGhee to listen to, thanks Stick.

Speaking of fathers, Arlo Guthrie and Bob Dylan sound similar to each other because they were both emulating Woody Guthrie. But Dylan also emulated others with results I like better, e.g. Tom Ashley ("The House Carpenter").