Reality
IOMfAtS
All good fiction is based upon reality.
I wonder if that is really all I need to say about the topic? Let's let it stand for a moment.
"But my story is about magic!"
So it is. And the magic is really only five percent or so of your story. The balance has recognisable relationships, geography, language and all the rest. Trekkies will acknowledge that Star Trek works because of the reality in the shows. We can argue about plot and production qualities all we like, but look at the reality. Harry Potter works because it is grounded in reality.
Your story's world has gravity, physics, love, romance, sex, people of various flavours, some with interesting abilities, others without. It has vegetation or desert, buildings or not, and is 100% familiar even in unfamiliarity. We can picture ourselves there.
The people in your story live in hierarchies, have problems, have wishes, hopes, dreams.
We can suspend our disbelief for the five percent of strangeness provided we stay with the things that are real to us. That is as true with SciFi as it is with a thriller or with romantic fiction.
And that is what I mean when I say that all good fiction is based upon reality.