The trailers aren't what made The Fall Guy a mediocre movie, not really worth sitting through. My guess is that's what hurt its box office performance, not the trailers.
I know for me the fact that they force me to watch straight-up commercials before the movie greatly detracts from my enjoyment. Movie trailers at the theater are one thing, but making me watch an M&M or fuckin car insurance commercial definitely kills the vibe. I completely avoid that shit at home. Why would I want to pay $100 to be subjected to it at the theater? I know the average person doesn't give a shit, but people like me do, and it heavily impacts my enjoyment at the theater.