I know, it’s the writers choice how things went, and I credit it them for doing it. But goddamn, when did optimism and potential turn into cynicism and despair?
Optimism doesn't always mean sunshine and roses. Optimism is most important when things are dark, when you need a ray of hope that things can get better, or at least that your own sacrifices make a positive difference for others. Think of "Yesterday's Enterprise" and the sacrifice the alternate E-D crew made to ensure that the E-C crew got back to where they needed to be to save their timeline. Was that cynical? Did you feel despair when Picard made his big history speech or leapt heroically over the railing as the music swelled? This is the same thing writ large. According to Coda, the canon timeline we now see on TV owes its continued existence to the bravery and sacrifice of the First Splinter characters.
Which can be read as a metatextual statement, a metaphor for how the fans' support of the novels and other tie-ins over the years helped sustain the franchise's popularity. And how the novels also started the career of Kirsten Beyer, who's gone on to contribute in major ways to the current screen canon. So the novels have had an influence on the canon even if it's subtle and largely invisible. The trilogy's events can be taken as a metaphor for that. It ended, but it still had an enduring impact.