See, but do they? Because Bucky Barnes has died, like, how many times and keeps coming back. Plus, Spiderman was one of the ones who disappeared at the end, but we know there's more Spiderman movies coming. Not to mention the there's no way Thor survived that and Loki didn't. And don't even get me started on Gamora.
Loki died at the beginning and not the same as the others. As for the other deaths ... the inrerwebs has spoilt a lot of shock nowadays