One of the main criticisms about the MCU is that the consequences of major events are hollow or somehow magical fixed/okay.
Death in comics is cheap and every superhero fan knows this. How many times did comic books kill a hero for shock value and to sell issues? Why did DC kill Superman in the early 1990s and break Batman’s back at the same time? To sell comics because they knew that people would buy it just to see if the characters actually died. Heroes in the comics come back to life. In order to make the events of Avengers: Infinity War and Avengers: Endgame have a gravitas, have a purpose and not be just for the shock factor, certain characters should stay dead after Endgame.
Any character killed before the Snap should stay dead. Gamora, Heimdall, Vision and Loki should reasonably all stay dead because they did not disintegrate from the Snap. Gamora was sacrificed by Thanos to retrieve the Soul Stone. As much as I love Gamora and want to see her in future Guardian movies, why kill her if they were just going to be bring her back. Heimdall was killed sending the Hulk to Earth. With most of Asgard gone, he should stay dead too. He wasn’t a major character except in Thor’s movies, but he was an important one.
Vision was killed after the Mind Stone was taken from him by Thanos. How will he come back if he was powered by the Mind Stone? Who in their right mind would want to use the Mind Stone again after the mess of Infinity War? Loki died in an attempt to shank Thanos. Loki might be only one that I wouldn’t mind not staying dead because Loki has “died” twice before (once in Thor and once in Thor: Dark World), but the others definitely should stay dead, no matter how much anyone loved the characters.
As for the Snap victims, it’s harder to say because we don’t know what exactly the remaining heroes will do in order to defeat Thanos and save them. I think it would be a rather poignant decision by the Russo Brothers if they decided not to have everyone who died in the Snap come back. No plan is perfect. Don’t get me wrong, most of the Snap victims should return, but it mean more if some do not. Heroes can’t save everyone despite their best efforts. Also, this is a really good way to get rid of characters that Marvel isn’t going to do anything else with in terms of shows and movies and side characters that don’t have a big role.
I would like Marvel to focus on the people returning from the Snap dealing with the aftereffects, but that’s for post-Endgame movies. In addition I’m sure we all have our picks on who will die during the events of Endgame. Two of everyone’s top picks are Steve Rogers and Tony Stark. If a major character dies through the process of attempting to defeat Thanos during Endgame, they should also stay dead, especially if they died in a heroic sacrifice. Heroic sacrifices should mean something.
Major deaths need to stick. As much as we all wish for an everyone lives scenario, it would cheapen both Infinity War and Endgame events.