That's exactly the anthropomorphic bias. Why wouldn't it be a huge mycelium? How do we even know there aren't types of life-forms made of structures that current scientific theories wouldn't consider possible?
More so it's entirely unclear why the life should have to be intelligent - or intelligent in a individual-animate-tool-building-animal kind of way.
> And even if you were designing a life form, it's hard to get creative with the "features".
It's hard to get creative, because creativity after-all builds from experience, therefore our imagination of alien life is still derived from the experience of Earth.
For that matter I'm very unconvinced that even Human civilization or life (should it survive for another 10,000 let alone 100,000 or a million) years will resemble anything like the organic individuals, with similar interests (i.e. space-travel, colonization) as it has today.