To me it sounds like the studio put some requirements and requests on the writing team that they were unable to put successfully in a coherent story.
If they hadn't had the requirement to include 10 minutes of TOS at the beginning or for Shatner to have a 'meaningful' role then may have been able to have a good movie there. Who knows.
The TNG production team were forced to include elements from a series they didn't respect (TOS) who they didn't understand or want to understand and ended up with me having to watch Kirk dying on a bridge after a fight with two other old men. All the good characterisation that Picard had earned up to that point was wasted and he ended up looking lame.