I always felt that humanoid aliens were also a way to get the audience to more easily emotionally connect and treat them as characters. Its hard to portray a truly alien lifeforms with alien behavior like you would find in a speculative evolution fiction art book while also giving them a human understandable emotionally driven narrative and space age tech for the plot of a story. Its easier to relate to blue cat person than to the Blob I guess is my point.

I really like the comic Humanity Lost for its better representation of alien life in its story. The author really cares about that kind of world building ad im here for it really great stuff.

i mean it seems to me that aliens are likely to either be completely different from us or remarkably similar, depending on their environment.

Like look at how things on earth look: stuff in the ocean is either a fish or something completely unique and fucked up, and on land we have a series of ecological niches that reappear across time and location to the point that it's kinda hard to tell the different incarnations apart.

I don't think it's that unreasonable to expect the odd humanoid alien, we should just also expect a bunch of them to be crabs and slime molds and fish.