Did Climo have a strong forehand, or roller game? I admit I don't have much experience watching Climo play but he seemed to be primarily a backhand player in what I have seen. Paul to me doesn't have any glaring weaknesses. So Paul = GOAT to me
Did Climo need a strong forehand game? No, he didn't. He dominated without it (he did have a killer roller game, BTW). Few players in his prime had strong forehand games (Stokely and...?) so there wasn't much value in developing it.
The modern game requires a more rounded arsenal of skills because more players have good backhand and forehand games, hence Paul has developed his to each be significant weapons. Put Climo in the same environment, with the same warp-speed, fat-rimmed drivers McBeth and company are throwing and he probably develops a forehand to go with his pinpoint backhand.
It's like saying that Mike Trout is greater than Babe Ruth because he's fit and well-rounded, despite the fact that he's benefiting from knowledge (nutrition, etc) and technology (workout equipment, video for technique refinement, etc) Ruth never had access to. The comparisons are, as others have said, apples and oranges.