Qui-Gon and Obi-Wan dying in the first two trilogies serves the narrative in the subsequent two films in their trilogies.
I believe Han, Luke and Leia’s deaths serve the narrative just as much. Han dying furthers Ben’s arc, as he goes deeper into the dark side after killing his father - taking that extra step - but is also more conflicted. Rey also loses her newfound father figure and it gives her good reason to hate Kylo Ren on a personal level in the next film.
Luke’s death doesn’t serve the narrative as much - he could have survived into the next film. However, there’s nothing edgy about it. Luke’s death is symbolic of him putting his trust in Rey and passing the torch down to the next Jedi; I also find it beautiful that he dies just as he regains the inner peace and heroic purpose he’d been missing for many years.
Leia’s death is the short term cause of Ben finally turning back to the light. He realises how much he is moved by her death, showing him that despite his best efforts, he too is ‘vulnerable’ to love just as Vader was; he also realises how much he feels he should carry on what she fought for and give up his identity as Kylo Ren. This is strongly implied in the scene with Han’s ghost/memory/vision thing.