"Freedom from want" in the sense of having everything that you could possibly desire is, of course, impossible by definition. There's all kinds of intangibles that will never stop being wanted. There are also unique material things that cannot be had by more than one person. You and I both can't have the original Mona Lisa. It is impossible for everyone to have a beachfront house in Hawai'i. We can't all be space admirals. If that's your definition of post-scarcity, of course it is a pipe dream. Even Grandfather with his reality warping technology couldn't have everything he wanted.
Post scarcity is normally used to mean that staples like food, housing, healthcare, clothing, and the like are not contingent on "earning" them. It means that people are free to pursue their interests and do the things that they enjoy without concern that they are going to starve or become homeless as a result. I am not going to be guaranteed happiness or to be a successful youtube influencer, though I could at least be a full time youtuber without starving to death.
It is generally more difficult to run a game from a basis of post scarcity, because we don't have any experience with it or any agreement on what its parameters are. Most, though not all, depictions of it are dystopian: everyone's a Reaganite welfare queen. Star Trek tends to have this problem regularly. Roddenberry wanted it to be post-scarcity, but the writers often struggled with creating stories within that structure. Not that there aren't any, but the constraints you'd work against to create the conflicts are amorphous.
Traveller does not assume post scarcity. The Third Imperium is frankly bordering on dystopian in the level of corruption and nastiness it tolerates despite the resources it has. That makes is rife with adventure.