Do we still need a star?
No, we have one in Rudy Gobert.
Do we still need that go to guy who can take over at the end of games?
Yes, unless 1 of Burks/Exum/Hood turn into that go-to scorer (which I don't see happening- not to say they won't all be good offensive players), we still need someone besides Hayward who can take over offensively at the end of close games, especially in the playoffs. He doesn't necessarily need to be a star, though.
Should we still do everything possible to try to get Russell?
Yes, depending on what you mean by everything possible. Although his recent play has been lessening what I would be willing to trade along with him, I would trade Exum for Russell (love Exum's long-term potential, just think an offensive minded/good passing guard fits better with GH, DF, & RG than a defensive minded/good passing guard does). I would also include a future pick, if necessary (OKC/GSW-maybe both), not sure about this year's pick. First choice would be to package this year's pick, both OKC/GSW, & another future pick or Burke to a team like PHI at #3. Everything possible is probably what it would take (Exum+this year's pick+OKC+GSW+future pick(s)+maybe even Burke or Hood), in which case I definitely would not do. As much as I think Russell is exactly what we need (#1 scoring option), it would likely take a massive overpay to move from #12 to #3. Because of this, I think we should hope Hezonja slips to the #6-8 range & try to move up for him as he is the closest thing to a #1 scorer in this draft after Russell.
While I do think that we can compete for the playoffs for years to come with the roster we currently have (+ this year's draft pick & a solid role-player or 2), I think the difference between this team competing for the playoffs & competing for championships will be that go-to guy who can take over at the end of games, as it's beginning to look like we have a championship caliber defense. Now, all we need is our Rudy Gobert on the other side of the ball & we will have a potential dynasty.