What if the aliens come and we just can't communicate? (opens in new tab)

That assumes they have a sense of sight similar to our own. What if their only well developed sense is smell; their equivalent of writing is depositing scent onto paper and their "non-verbal" movements were the movements required to produce, project, and receive, scent? How would we "look" to them? What is to say that they share any senses with us?

If they are blind, and communicate via pheromone symphonies?

If they are jellyfish with tentacle exchanges of salts?

If they are crystalline and ring with resonances in the audible and radio ranges, with phase shift memes and holographic memory payloads?

We've seen too much Star Trek with rubber-suited humans, speaking with different nouns and calling that 'alien'.