It’s clear after seeing this movie that they didn’t work with a script; it seemed like they were simply recording whatever happened on set, and I later confirmed that was indeed the case. This explains why so many moments feel hurried or unfinished, most of the visual effects appear underdeveloped, and the presentation of "Deadpool" was pretty bad. Despite all this, surprisingly, it's not the worst installment in the X-Men series; it just establishes a very low standard.

Source on TMDB