Users on this subreddit love to complain about how full of spoilers trailers are these days (though spoiler filled trailers have been around for a long time).
The main reason trailers have so many spoilers is because the average audience goer wants to know exactly what a movie is about. This isn't because audience goers are stupid, it is because most people don't have a lot of money for entertainment. So, they want to make sure they are not going to waste $20+ on a movie they will hate.
I think movies like mother! and It Comes At Night trick audiences and will increase the amount of 'spoilers' in trailers and press releases. People who hate spoilers should prepare themselves and avoid trailers.