What changed?
Below I've embedded the new trailer for Project Almanac as well as the first one for Welcome to Yesterday. It looks to me that the new marketing strategy is to disguise -- or at least not emphasize -- the found-footage angle. The story is the same: high school students put together a time machine, change recent history to their benefit, and then must fix the damage they've unwittingly caused.
Over the years my enjoyment of found-footage movies has steadily decreased, so I grant that I'm not the best judge of the material, nor am I part of the target audience. But the new trailer looks more intriguing to me, even though it uses much of the same footage. If you like found-footage movies, does this one look any different to you now?