I agree it could have went great for the original show although I never really considered the actual Powerpuff Girls experiencing muscle growth since they are well... very minimalistic. However, I never considered Princess Morbucks for it either but after revisiting that scene from this thread, I can't get over how well done it was. Now. I'd love to see the original PPG experience growth portrayed in that exact style.
But yeah, like most of the reboot that episode was very disappointing. It's funny because I was hoping the new PPG had another well animated slow motion sequence from the exact same episode with Princesses growth but their portrayal of slow mo failed very early on.
Mo Job is starting to look like one of my favorite episodes of the original PPG, having so many scenes I just love. I wish the reboot took at least SOMETHING from it.