They revere Joseph Smith for sure (and some other made up folks like Moroni or whatever) but I think it's incorrect to say Jesus has taken a back seat in their faith. I just toured one of their temples (which they allow only briefly before they consecrate it), JC was everywhere. Not sure I saw any imagery of Joseph Smith, but it was a lot to take in and I may have missed it.

Atheist here, but grew up mormon: Jesus is definitely the main character. I'm hazy on the details but it's even mormon canon that a lot of events in the old testament involved Jesus in pre-birth spirit form (or something idk), or were at least analogous to his life. Joseph Smith and Brigham Young are to Mormons as any notable dead pope is to Catholics - revered, spiritual authorities, allegedly could talk to god, but they're not worshiped and they didn't come up every Sunday, they were kind of in the background