A lot of the Hayes Office rules were ridiculous but I think they resulted in writers and directors being a little more creative and insinuating things rather than showing them. That's not to say that some films didn't suffer because of the code. I think "Rebecca" suffered, not irreparably, but it would have been a better film if a certain major plot-point hadn't been changed.
In my opinion the actor whose career appeared to change the most because of the code was Norma Shearer; she successfully shifted from sexually liberated contemporary women in her pre-code films to noble heroines and period dramas after the code was put into effect.