Maybe get a better player development coach? Or just a better coach. Milwaukee turned it around in a year with practically the same roster.
That isn't all that true. Yes Giannis, Middleton, and Bledsoe are all still there (along with Brogdon and Snell), but the rest of the rotation is different and Giannis keeps getting better and better.
Remember the Bucks had Jabari Parker, Thon Maker, Tyler Zeller, Shabazz Muhammad, Matthew Dellavedova, John Henson, Jason Terry, and Brandon Jennings play in the playoffs last year and many with key roles.
They swapped all of those guys for Brook Lopez, Nikola Mirotic, George Hill, Ersan Ilyasova, Pat Connaughton, Tim Frazier, DJ Wilson, and the injured guys of Pau Gasol and Donte DiVincenzo (and Brogdon just came back).
The simple truth is the Bucks totally revamped their rotation by adding better fitting pieces and more complimentary players. They saw what they needed and went out and got players to fill in those holes. They aren't even at full strength yet as Brogdon is just coming back, Snell isn't yet at full strength either, and they still don't have Gasol back (DiVincenzo is so deep on the depth chart I'm not sure he matters).