Exactly. The trailer has one specific job, to lure you into seeing the film. But it doesn't guarantee a quality movie. You have to sit down and watch the movie from start to finish, and that's the only time you'll know if it's quality. A trailer doesn't guarantee anything, only if the images and concept interest you (or excite you) enough to see it in the first place.
So to me it feels like conclusion jumping, when an excited fan thinks a good trailer means the director is going to nail the characters or nail the movie as a whole. Especially since "character" is Snyders weakest point. Even if you love most or all of Zack's films, he lacks a bit of focus when it comes to character and writing.
Comic book adaptations are also really tricky, especially when you're working under a huge studio with so many people wanting specific things for a growing franchise/universe. Argo writer or not, there's no guarantee that even Terrio will "nail" the characters. It's one thing to write a script for Ben Affleck's new film. It's another thing to collaborate with DC and Zack Snyder for a Batman vs Superman movie that has to tie to multiple Justice League movies. Directors and writers have a little more control for DC than they do over at Marvel, but it's still different than writing a one-off for Argo.
Ill believe it when i see it. If im impressed, ill show it after i see the movie. After watching the trailer multiple times, it doesn't convince me than im getting a good movie. It's just showing me that Batman will look a lot cooler than i thought a couple years ago. And that there's a chance that it could be a good movie.
I don't think i've ever seen a piece of **** cheesy trailer and ended up seeing something great though. But i have seen a massive amount of great trailers turn into average or below average films. Prometheus was one of the best trailers of the last decade (maybe i'm exaggerating, but i remember being pumped). The movie was average at best with some good things but a ton of dumb **** too. I felt like it wasn't necessary.