The growly thing is just a direction music took. The rock and metal genres are constantly being pushed beyond existing limits, in one way or another. And perhaps growling taps in to something primal. Perhaps man kind could grunt like that before learning more articulate speech and singing.
Anyway, every generation experiences a lack of connection, at some point, with later music. It just "is what it is." There are so many factors that play in to what music one is drawn to and accepts.
A big part of it is what one's friends or potential mates/lovers are listening to and excited about. It's a common language and interest that can draw you together and give you connection.
Anyway, that's my take on why some accept growlies. While I do not prefer them, in the vast majority of cases, I do find them tolerable sometimes and appropriate to the music.
On the other hand, if I thought about it, I could cite singers that others think sound beautiful and very pleasant, but I think they just sound gutless, spineless and saccharine.
No accounting for taste, right?
P.s. what is your view of the "caveman" sections of various Mike Oldfield recordings (in particular the TB series)? Isn't that fun and interesting?