The real alien people, and everything humans think about them, are not the same thing.
In other words, they are real, but what humans think about them is not real.
Well, they are people.
Males and females.
They get born.
They might get sick.
They are not perfect.
They have a natural life span.
The same as us.
The individuals that travel to other worlds, like those who travel to our world, are the professionals of their races.
Not just anybody on a world travels like that, to work between worlds.
The alien people are working here, and they maintain professionalism with us.
But yes they can get mad.
The alien people look different from us, but still like people.
They all look different world to world.
We are all alien to one another, all different.
Our bodies literally are made out of our own worlds.
And fit our own unique atmosphere.
Chemicals, minerals, elements, germs, air pressure, gravity, light, everything.
A race can't just go to another world, and breathe and walk around there.
Everything is "alien" or foreign, or hostile biologically.
The advanced races that are already traveling to visit their neighboring worlds have advanced ways of meeting together without exposing themselves needlessly to one another's atmosphere.
But, when they do that here, with us, it looks like magic or something to us.
So we start to imagine things.
They use natural abilities that are just further evolved than ours are yet.
But they also use technologies beyond ours yet.
Supernatural is really just natural.
Also, advanced races already know each other and share a lot of knowledge.
Each race has many benefits we don't have yet.
But we will.
All of them do it.
So we will too.