Hmmm, I guess we might have different interpretations of the philosophy being discussed by the narrative? I experienced Endwalker as an exploration of both whether and why life is worth living in spite of its many hardships, which at least to me is a complex and challenging question. My personal interpretation is that Endwalker didn't provide an explicit answer to that question, nor did it intend to; rather, it presented a lot of ideas and arguments that act as catalysts to propel individuals engaging with this question towards whatever their personal conclusion is, while also showcasing a variety of different conclusions to this question from the characters in its stories. Though while Endwalker doesn't explicitly answer why life is worth living, it does have a hopeful and positive outlook that clearly intends to guide players towards a specific answer to whether life is worth living.
While the power of friendship was certainly championed as a tool with which to overcome hardship as well as one potential source of joy, I don't think the narrative positioned it as the answer. After a lifetime of sociopathic genocide, my friendless Zenos obtains what makes him happy, and while the narrative is clearly critical of his methods, my reading of his story's conclusion is that he felt all the hardship was worth it to reach that moment. Venat always loved life for its own sake, being a lone wanderer who enjoyed not only her interactions with other people, but her interactions with the world and all of its wonders. And perhaps more telling, she sentenced everyone she knew — both friend and foe — to death, committing genocide on her entire world, because after weighing her many options she felt it was the right thing to do. Whatever meaning and value Venat put on life extends well beyond friendship. Hermes deeply struggles with what he sees as cruelty and apathy committed in his society; these are valid, tangible problems, and the narrative doesn't imply that friendship would have solved them.
The question about what makes life worth living is a complex, subjective, and personal one, and if Endwalker had proposed one answer to rule them all, I agree that it would have felt hollow. Thankfully, I didn't feel like that was what it was saying. Though again, that's just my read, and I don't want to invalidate anyone else's.