The primary purpose of representing aliens (extraterrestrials) is not to describe them, but instead to describe humans. This is why:
Aliens are overwhelmingly, nearly 100% of the time, described as being humanoid, although there’s no rational reason for assuming them to be humanoid.
Aliens are usually represented as relatively emotionless but highly intelligent. This most likely reflects the Cold War vision of the West for the Soviets. It’s not even true that they must be intelligent to reach earth, given what little we know even about intelligence, much less about how that applies to aliens.
Aliens are, again nearly 100% of the time, described as coming to earth or otherwise travelling through space in spaceships. Mostly this is because when humans travel in space they do so in spaceships. This hardly implies aliens of which we know nothing would do the same.
Aliens are often described as having a hive-mentality, hence the term “mothership”. This is an embarrassing reference (or it would be, if Westerners ever did any self-reflection at all) to the West’s concept of the Soviets during the Cold War.
The “debate” among those who descrbe aliens often centers on whether they “come in peace”. So they are either described as having advanced weapons and an eagerness to use them, ala War of the Worlds, or as some kind of scientists doing research, ala “alien abduction”.
The effect of all of this nonsense, fantasy, and irrationality is to dull human curiosity for learning about actual aliens. The only way that humans are likely to experience aliens (the way that maximizes the chances of experiencing them) is to explore space, both manned and unmanned. The more that humans can be brainwashed into thinking they know aliens, the less likely they are to want to actually know them.