Obito is very important as he´s the one who shaped the lives of the two mains and kakashi.
As someone said before kakashi was a prick before obito changed his life and ideals, kakashi was a prick obsessed with the rules and obito changed that, he was the one who taught kakashi his motto "people who dont folow the rules are scum but people who abandon their friends are ever worst than scum" and that motto was eventually passed down to naruto himself, also obito got crushed by a rock because he saved kakashi and was left there to die, so kakashi took the resolution to never abandon his friends anymore, besides kakashi adopted a lot of obito´s traits over time, like being late, being laid back, obito was kakashi´s hero to the point where kakashi spent all mornings going to visit obito´s thumbstone to pay respect to obito, besides the obvious fact obito gave kakashi his sharingan which made him famous and gave him a great powerup and put him above the rest.