Oh my god, is this anime dated. The animation is awful and the plots range from generic to ridiculous. But I love it.
When you start watching this, you have to remember that Ribbon no Kishi is the Ur Example of shoujo. It was revolutionary and genre-defining for it's time; most shoujo series that came after have been inspired by or deconstructed the elements Tezuka introduced. To truly appreciate this anime, you need to watch it as a study rather than expecting something refreshing or deep.
Like most classic anime, the animation was done on the cheap. Cells are blatantly recycled (even from the intro) and there are long, artificial pauses that make the characters look like they're spacing out between lines. The bad 70's English dub available on Crunchyroll doesn't offer any improvements, though Nylon's voice is fun to hear.
All of the characters are idiots. Every single one of them! Most of the plots get rolling because someone missed something obvious and did something very stupid. But that's classic Tezuka, and there are moments where silly things happen just for the sake of silliness. This is fine; this is a kids cartoon from an era where animation was meant to be spectacle. It's a mishmash of fantastic tales where, even if the conclusion is obvious, the path the characters take towards it is unpredictable.
If you already appreciate classic anime or are a huge Tezuka fan, definitely give this a watch. If you love shojo anime and want some insight into how it began, try a few episodes. Everyone else, well... you're probably better off checking out the manga or reading the plot summary on Wikipedia.