I believe it's a movie you can't fully appreciate on a first viewing. I certainly had a similar reaction. It's definitely a slow slog, compared to more modern movies, and has some artsy flare some might not appreciate. But if you view it more in the context of when it was made it might make more sense. Trying to demonstrate a realistic view of space travel, considering landing on the moon didn't happen until a year after the movie was released. Somewhat forward thinking when they were blasting tin cans into outer space. Also surprisingly relevant the rise of Ai and how perverse and different the logic would be from humans or humanity. Add on the sci fi elements about Jupiter, was thought provoking. The last half builds up nicely for me.
Yeah fast forward to today, and all those concepts seem pretty well played out and overly familiar, and the level of visual details in movies is outstanding. Plus we all have super computers in our pockets which can take some cool photos. So the movie seems over simple by todays standards, but that is almost 60 years of evolution right there.