Not so sure about the future Hall of Famers: basketballref gives Gobert a 26% chance and Mitchell - 13%. But the question was not about those two players: you CAN be a contender with them two as your biggest stars. The question was that the Jazz could not improve their supporting cast: they had no picks and could not get much for Bojan (33), Conley (35), Ingles (35), Royce (29). All those players and the 30-year-old Gobert could only decline.
The Cavs, on the other hand, could easily continue building around really young Mobley and Garland: both Allen and Mitchell can get them really good players in trades.