The focus is really on the Skywalker family. I don't think we need to discriminate between Skywalkers... they are both utterly vital and the centrepieces of it all.
You could remove other charatcers, and the story would be told differently. But remove either Skywalker and it is NOT thje same story; it is some other thing.
But meanwhile... Obi-Wan is the man,. Even more so for his failings- and it must be said, his was not the only failure. Let's not let Yoda and even Anakin himself off the hook hear.