As a general rule doubled pawns are a hindrance to you.....but like so many questions in chess, the answer depends on the position.
Say your opponent has already castled. Stacking your knight pawn on the bishop pawn can open a file for your rook to bear down on the opponent's king.
Even on the other side of an opponents castled king, rooks need open files to operate to their best, and often doubling your pawns can give an unused rook some air.
So don't regard the doubled pawns=bad as a hard rule.
Will you usually make a trade that "stacks" the opponents pawns, usually on the bishop file?