No team hits 100% of their free throws. The Blazers were the #2 free throw percentage team in the NBA this year, shooting 81.2% on average. If they had shot their average tonight, they'd have hit 22 of 27 free throws instead of 20. So, still a loss, just 2 points closer.
Overall, the issue was their defense. They played decent defense in spurts when Jokic and Murray were off the court, but they didn't get stops when the Nuggets had their starters out there. Slowing the Denver attack, especially on their home floor, is going to be a tough ask. But the Blazers kept it close with their own pretty strong offensive showing. If they can at least slow the Jokic/Murray tandem, they have a great chance to steal one in Denver.