This, like other movies, I think comes down to novelty. Some of the shit done in that movie was truly incredible… At the time. Some bits are still really interesting.

The jogging scene, for example, was done at a time when CG wasn’t really an option. So then you ask the question… How did they do some of these shots? How is this guy seemingly running in a zero g circle but it’s actually a real camera?

Cinematic transitions are another. The bone spinning into the space station was really cool. It’s a shot that has permeated like every form of media. Now it kinda looks cheap and jarring.

HAL as an AI, an evil robot, was an extremely interesting. Now it’s something that has been done so, so many times since.

As a sci Fi I still like it, the slow pace isn’t something that bothers me. I enjoy movies that are capable of taking their time. So many movies move at breakneck speeds. The plot is really cool to me as well.

Otherwise, yes, it’s not surprising that a modern audience finds this incredibly boring for all the points above.