If there was only bad dialogue, I could accept it.
If there was only low-budget looking FX, I could accept it.
No, the worst thing about the movie was this: It was boring.
I was looking at my watch by the end of the first hour. SO much talking and attempts at showing emotion, etc. The motivations they cart out for Logan seem absurd and you'll be even more angrywhen then throw a "shocking twist" at you towards the end which makes even less sense and shreds up what little credibility the film has.
I have no issues suspending disbelief for movies. But since X-Men 1, the bar has been raised. Fans shouldn't have to settle for this shoddy work anymore.