While in the original Aerith's death was a big moment, and it delays the progression of the story as the party struggles to decide how to save the world.
Honestly I loved this part of the story because it actually shows them grieving a bit. I hate how some games makes their characters be these macho characters who just shrug it off when one of their friends die.
Yeah, I love it that part too... Too many RPGs, including games of Final Fantasy series don't have characters deal with death as reasonably as FFVII does.