The plot is about:
- A spaceship travelling through the universe
- Earth is a rogue planet whose inhabitants have been cut off and don't realise that their true purpose is to be part of the spaceship
- The reason earth was in turmoil (wars etc.) was that they didn't realise that their true role was to fit into the ship
- The ship contained 3 or 4 beings that made the thing work
- Planets throughout the universe are populated with the various beings which are components of the space craft
- I seem to remember like an eye shaped being
- Each of them fulfil their role
- Humans are part of that as well.
- There are loads of planets with humans on but earth has gotten overlooked so it never realised that's what they were designed for
The story concludes with the ships picking up someone from Earth
- and with the "human" realising that this is what they should really be doing
Humans have a different name that explains their role in the ship.
I probably read it around 30 years ago in English in a sci-fi collection book.