I mean, these characters will be back, obviously. Yeah, they're some of my favorites too, but if Marvel can ruin other classic deaths (Like Bucky, Elektra, Captain Marvell, etc.) and people can get over it, what's the difference with this? Almost anything in comics can be undone. Killing off characters hardly ruins the Marvel Universe, and if the direction is unpopular, then they'll just change it back.
Killing them off destroys their mystique thus ruining the entire concept and pretty much the bedrock of the Marvel Universe.
It's completely irrelevant that they'll potentially be back. If anything, them coming back just makes it all worse.