It's because they don't have a legitimate superstars who could carry the team consistently. Also, because the lack of maturity in decision making on and off the court. Give them a veteran superstar and a seasoned coach then you will see a different trailblazers playing on the court.
It's not a mandatory for them to have a superstar or a seasoned coach. Just a role players is enough and that's what their lacking. But still with their setup, they can finished a good spot on the West. Example last season, they performed well in the West standing and finished at 3rd spot. But unfortunately got swept by the New Orleans Pelicans in first round of the playoffs. It's fine if it's not a sweep but they literally choked on that game.
Competition in the West is tough but they managed to get a good spot last year so it means that their current lineup is good. It's just that they are pressured once they are on playoffs and that's what they need to changed as they supposedly not new anymore on that kind of pressure.