Refs in Europe help to bigger clubs due to money for Uefa.
Uefa wins more if big rich teams and famous players play in finals.
Or: in qualifying rounds, it is better for Uefa if Arsenal/Man Utd qualify instead of losing to a random poor team from Prague, Krakow or Tirana.
In Spain, refs help to Real because "Catalonia is not Spain" and Barcelona is openly against them.
More or less, Catalonia wanting independence is stabbing a knife at the back of all Spain the same as when I say that Messi is not that good anymore or when I talk bad against Pep.
That is a tribal thing.
You can't go against a tribe and fundamentals of that tribe and expect good things in return.
So, refs in Spain are not bad.
They aren't making random mistakes.
They are on purpose on Real's side due to politics and Catalonia's independence.
And that will change only if Barca moves to another league or if Catalonia drops independence ideas.
So: it will never change.
And don't dream or hope about fair refereeing.