2001 is pretty damned hard to follow, mostly due to the bookends of the film, with the prehistoric opening and incredibly trippy closing, which serve to bewilder many viewers. The bit in the middles is juts fine, though. Kubrick was famously exacting in what he required from his films, and the slow pacing is entirely intentional, and so too is the requirement that you as a watcher actually have to think and interpret what is happening, and not have it handed to you on a platter. The transformation into the Star-Child — and proceeding bad trip through space — is definitely obtuse and was designed to be open to interpretation. My personal view is that when Bowman activates the monolith, he’s whisked to an alien zoo for observation, before they ascend him into a new form. But hey, that’s just me.