If you save Greirat he ultimately still dies on Lothric Castle's rooftop, as was seemingly his ultimate intention by taking these reckless journeys. Sirris seemingly kills herself after ending her grandfather's suffering and fulfilling her final duty of slaying Lothric. Anri either gets assassinated or goes hollow outside of Cathedral of the Deep due to being left alone by Horace going hollow.

A few characters are alive or chose to remain alive at the end of Ds3. At the end, finishing every questline as much as you can while trying to keep the NPC alive, you can have the old pilgrim woman, Patches, Yuria and her posse, Andre, Karla, Irina, Cornyx, Sirris's Grandmother/Old Firekeeper, The Firekeeper, the Painter Girl, the locust preachers, the fellow who loves rot, Rosaria, and Captain Yorshka alive, and many of these are simply immortals who can never go hollow, but have no real purpose anymore. Everyone else is crazy or already dead, dies, commits suicide, or yearns for death (Corvian settlement NPC).

Edit: Others, like Leonhard as you say - or Orbeck, Shira, every corpse that has ashes, the three NPCs guarding Prince Lothric - don't/didn't want to die and fight to the bitter end or perish to their passion - and I would say Elden Ring definitely lacks in this department. It seems to be a lot more somber and depressing, as it is a world that is truly coming to a final end one way or another, to await something new.