If he'd stopped after one, it would have been fine. He decided to do a series. It got weird. I still read them but the original is a decent standalone and you won't die unhappy if you never read the following.
The same could be said of 2001.
Officially, all the Rama sequels were co-authored by Clarke and Gentry Lee. Clarke claimed that Lee did virtually all the writing and he was only a consultant, although AFAICT the only source for this claim was in an interview many years after they were published, presumably after Clarke was aware of their negative reception, so who knows how much of that is true vs. reputation management.
But yeah, they're awful. I read them when I was 12-13 and it was one of my first introductions to the idea that sequels to great books could be so bad (and then for some reason I went on to read the Brian Herbert Dune prequels, which are even worse). Read the first one, and pretend it stopped there.
I thought 3001 was fine and a good conclusion.
Although it seemed implausible in the setting that humanity wasn't immortal given some of the technology.
2010 is also good. The movie is also competent, but it could never fill the shoes 2001 left.