Gobert has been fantastic defensively all year. He's still incredibly raw offensively, and no reasonable person should've expected him to markedly better on that end based on what he showed last year. His hands are still iffy, and he doesn't have any post moves. But he's gotten better with positioning, screening and he's still active on the offensive glass. The key for the Jazz will be keeping him totally healthy.
To your first point, Hayward at the level he played against the Clippers (or somewhat close to it) puts the Jazz in the playoffs for sure.
I don't think he has been as good defensively. At least not to the eye test. I can link you the thousand threads where people talked about him being one of the best defenders of all time. He just doesn't look the same.