That's because Carter is one of those "make it up as you go" guys. He is a terrible long-form storyteller, and he has no idea where his story is headed. Classic "mystery box" bulls***.
The standalone episodes were always fun. The mythology was fun back when I thought there was actually an explanation and connections behind all of the stuff. Eventually, I came to realize that there weren't, and Carter just had some neat ideas he wanted to play with. He's great at creating atmosphere and concepts, but he's crap at actual storytelling, because doing that requires that you have an ending in mind and that you know how to get there. Carter never got that.
Trailer is up. Sadly, it looks like they're leaning on the alien conspiracy stuff again. And poor Langly isn't dead, he's just been trapped in Mulder's smart phone all this time: