Yeah, it seens the Monster Ardyn got cut, and the world of Ruin would be like FF VI where you had to gather your party members:
Well, the first stop after Altissia had an (smaller) open world area and you could drive the car alone.
There was a level leading up to when you encounter the Shiva statue.
The dark world section of the game featured more enviroments, you encountered each party member in different locations and you could explore part of Lestallum.
The final boss (which was another Ardyn form) got cut early this year.
The Tenebrae invasion happened after the protagonist entered the city and you got to explore a very small section of the city and Luna's chamber.
Scenes that featured Luna got cut because they were considered to be problematic.
Cor got written out of the last half of the story since it made no sense for him to show up (he was Noctis companion during the small open area after Altissia).