The tone and humor of the Guardians films belong to Gunn, and the work that he did with that cast.
It was easier for Waititi to take over Thor after Alan Taylor delivered a lackluster Thor: The Dark World.
I agree with Taika Waititi 100 percent on this, and I imagine that many others feel this way, which explains why Guardians of the Galaxy Vol. 3 hasn’t found a replacement director yet (if ever).
Replacing James Gunn on the franchise that he helped mold and shape from square one would be nearly impossible.