It's proof that "stakes" aren't everything. Everyone who complains about these movies not having stakes is completely missing the point.
We might lose an Avenger or two but the audience knows everyone that got dusted will be back and they don't care. They're in it for the ride. It's whats actually important.
Comic book superhero deaths are rarely about just being shocked and sad that they killed off someone popular and loved by readers. It's about the trauma experienced by those who had to witness the death. It's about the void they leave in the world/superhero community and what other heroes decide to do to fill it.
At the end of Infinity War, the Avengers are forced to play out a completely unwinnable situation knowing full well that they will lose - and still give everything they have. It's the absolute height of heroic spectacle in the MCU. And when they do lose they're forced to witness their friends and allies expire in tragic terror and confusion.
It's clear to anyone familiar with the medium, as soon as T'Challa disappears, what was going on there. Yeah - these characters aren't dead for good and they're definitely coming back. And yet it keeps going and we keep having to keep watching heroes turn to dust. But it's not about them, it's about the heroes left standing and what they just had to witness. How they'll process it, what they'll do next. Steve's response to Natasha at the end of the trailer is just as impactful to me as the big CG-heavy moneyshot at the end of the Captain Marvel trailer.
It's an excellent premise for a movie and this trailer doing what it does makes it clear that people want a movie like this - regardless of the obvious outcome.