I never hated the PP strips (without Marcie). They often had this theme of unrequited love that she had for Charlie, but at the same time not knowing how to do anything about it.
She was the only character to have an actually hard life. She wasn’t very bright, felt she wasn’t very pretty, but she wanted to be. If you remember she lived with just her dad in another part of town that you got the impression wasn’t as nice.
She is a very misunderstood character I think. Insanely loyal and loving of her friends, wanting to be loved by Charlie, and always faced with failures outside of the venue of sports.
Marcie sorta bogged her down, but when she was on her own or especially with Charlie Brown she was a very likable character.