It's about more than simply having characters die, it's about tone, it's about setting, it's about vision.
People say Infinity War has been "epic" in dark ways, I haven't seen it, but even if it is that's one movie out of every other MCU movie which I have seen.
A scene like this was far more edgy than anything in the MCU. And once again, remember what I said, it's not just about people ending up dead or not, you can have a light hearted comedy that has death, it's about tone and the way it's delivered. Is there gravity to it? An honest sense of doom? Not in 99 percent of the MCU, and probably not in 100 percent of it.