Star Trek: The Motion Picture is, in retrospect, on of the strangest films ever made, pretty much by any standards. It doesn't feel very much like a post-Star Wars sci-fi blockbuster, feels at odds with the following original cast Trek films and by being one of the very first films based on an American TV series it's missing most of what would subsequently become the standard rules for translating something from the small to the big screen. So much of it feels very, very odd.
Now of course, it's slightly unfair to call a film odd just because no one had yet decided that the best way to do a TV based film was to completely recast it, throw in some heavy irony and give the original actors tokenistic cameo roles (the '09 film, despite not technically being a remake, otherwise shows how to do that sort of thing right). Nor to criticise it for not being more like Trek films as yet unmade. But, for me, this is one of the things I enjoy most about the film, it's different and a type of movie that would never, ever be made today. Arguably with good reason as it's deeply flawed in many ways, but at least that makes it more interesting to watch.