DCEU isn't really Snyder's fault, it's WB. Quite frankly, the WB Execs have no idea what to do with the DC properties, and they (without any knowledge of the comics) always get involved. Superman the movie was decent, but they interfered with Superman II, and parts 3 and 4 were awful. Although '89 Batman was a huge success, the reality is that it was made by non-comic fans (Burton was very proud of that fact at the time), and was partially a huge success because the only other live action Bats in anyone's recent memory was the 60's camp. We all know how that series turned out. Because the Nolan trilogy was a huge success, the WB execs seemed to think that all superhero movies should be "gritty" and heavy, and they made the mistake of continuing to hire David Goyer to write. The only thing the WB seem to do with DC characters is make terrible tv shows.
But back to Marvel, I don't see/understand the need to kill off characters either. The Marvel universe is so huge, and they've already shown with their own films, that they can do trilogies for individual heroes, without necessarily the need to add in anyone else. They could totally keep moving forward with their newer film heroes (Ant Man/Wasp, Spidey, Captain Marvel, Black Panther, Dr. Strange) after Endgame without killing off anyone. Just that group alone is good for 8 - 9 films. And that's without adding the X-Men, or any other characters...