The catch is, we simply don't know. We do not know if Solaris is a "superior" intelligence. We may guess it is an intelligence of sorts. There is also very little to suggest that it understands us in turn. My interpretation is that the phantoms were its effort to understand humans, and probably not a very successful one either.
Another fantastic book on the subject His Master's Voice, where a whole massive team of scientists tries to decode an interstellar signal. In the end, they didn't even prove it was a signal, and not a natural phenomenon.
Also - The Invincible. Probably the most western sci-fi styled book among his works, dealing with an interesting concept of mechanical evolution.
I have some opinions on that, but for the purposes of the story, I agree that the level of superiority of Solaris's intelligence is pretty much beside the point (or rather, the futility of attempting to parameterize Solaris's intelligence is the point). Maybe it's not even self aware. Maybe it's hyperintelligent but reaches conclusions in geologic time, or something. Maybe it's amused by us and would find the notion of communicating with us in a meaningful way silly.
On the topic of self awareness vis-à-vis aliens, Peter Watts' Blindsight is a recent classic.
Lem's work (at least Solaris) explored the intellectual inability of our species to communicate with a vastly superior intelligence. Solaris did not have any problem seeing what people were doing, thinking, signalling to it, and so on. It's just that what possible difference could it make?