I may be over-analyzing but that may not be our Steve, the one that we know.
Thor seems cautious and uncertain, when he sees Steve.
He uses the hammer to test if it's really his Steve.
Even when it works, Thor still seems hesitant and unsure.
Like he doesn't believe it or feels something is off with him.
In the previous trailer, Steve looks different.
After some reading online, seems there are fan theories.
1. This Steve in the new trailer is a variant
A timeline splitter. When the original Steve stays behind with Peggy, he alter history, creating a branched timeline, creating a variant of him. And it is this that caused the 'incursion' that Doctor Doom is exploiting.
The Steve we see in the new trailer looks like the Nomad look from Infinity War, while the the previous trailer looks like the one from Endgame, so the timeline is messed up as to which Steve this is.
2. This Steve in the new trailer is Captain Hydra
Like Robert Downey Jr playing the villain this time, as Doom. Chris Evans may be also playing the villain this time, as Captain Hydra. And he's working with Doom. They're together but on the other side now.
Some fans say that Doctor Doom's magic can allow evil variants to lift the Mjolnir, which explains why Thor looks shocked, rather than relieved or happy. He knows it's not HIS Steve that he knew.
So Steve Rogers may return in Doomsday but it may not be OUR Steve. And he's not returning as Captain America because Sam Wilson IS Captain America now.