Wasn’t magneto her dad?

That's a rather far-reaching and inaccurate statement. The overarching narrative of the first 23 films was that of Thanos' quest for the Infinity Stones, so of course they were addressed here and there, but by and large they didn't play a major role in many of the films. That's one of the great things about the MCU. Rather than cram everything into a few films, they were able to gradually build out their universe, and slowly merge many disparate narratives into one large finale.

Fourteen of the films had nothing to do with the Infinity Stones whatsoever, and many of the rest only dealt with them in a passing manner-- Captain Marvel gaining her powers from the Space Stone in a film that otherwise had nothing to do with Infinity Stones, or Wanda having her innate abilities enhanced by the Mind Stone in a film that was about something entirely different. Dr. Strange possessed the Time Stone, but his film was about an entirely different matter. Really, only the first Guardians of the Galaxy film, Captain America: The First Avenger, Thor: The Dark World, and Infinity War/Endgame directly dealt with the Infinity Stones.

Not really. Without the infinity stones you can still have the Arc reactor, vibranium, Cap's serum, Hulk's gamma experiment, Thor's hammer, Falcon's wings, Pym's particles, etc.

Though I would agree the MCU relies heavily on McGuffins. The infinity stones are the biggest ones.

And they even retconned the comics to make Magneto not their father anymore and also reduced mutants drastically... Bet they're regretting that now that Disney has them back, lol.