Even in books, where the limitations of costumes and sets are less relevant, most aliens are at least somewhat humanish. Though there are certainly some more exotic ones like the pattern jugglers, First Person Singular, or the Prime.
An aside, but Adrian Tchaikovsky‘s Children of Ruin/Time center on intelligent spiders and mollusks. Earth-centric as they were bio-engineered from Earth native species, but an interesting take on non-human species.
If we're name-dropping, the Vernor Vinge pack-mind dog things are another fun example of non-human races with actually non-human modes of cognition, even if they're not as far removed as Solaris/Revelation Space sentient oceans. In contrast, although I really liked A Deepness in the Sky for other reasons, the spiders ended up feeling way too much like humans in funny bodies rather than any kind of actual non-human intelligent species.
Really comes down to a lack of imagination. I imagine there's a good chance life elsewhere is unrecognizable to us as life. No id, no ego, just a vivacious electrochemical reaction bent on survival. Think viruses on a larger scale.
"Good chance" based on what?
The size of the universe, and our relative size within it.