This episode is one of the two best of all of science fiction television, both of them from Star Trek TNG. (The other is "The Survivors").
These episodes epitomise why science fiction is the best of all fictions, of all storytelling: The best stories are about people, and science fiction allows us to explore people in any imaginable situation, thereby providing the highest levels of insight into the human condition.
This episode is a triumph for the writers, Peter Allan Fields and Morgan Gendel.
In this episode, we see the importance of the gift of every day of our lives.
Picard is given a gift of an entire lifetime of experience, from the perspective of a doomed civilisation. Even though only 25 minutes passes on Enterprise, he lives and breathes in their world, and in their love and humanity, for, perhaps, 50 - 60 years, and comes to know and understand who and what they were; a gentle, loving and intelligent people.
Other than this lifetime of memories, the only trace of their lost civilisation is the flute he learned to play on their world, which symbolises the fleeting nature of life; a tiny crack between two great voids.