>>213938599 (OP)
The same thing that kills any other adaptation, a lack of understanding of why the original product works.
While there is no magic formula that would ensure success analyzing and replicating variables of previously successful products has always been the industry´s approach. But what is not understood can not be replicated.
You can get away with a lot of changes in adaptations but you need to at least be able to identify what core elements define your IP identity and you just can´t do without.
Gunn doesn´t understand Superman in the same way Disney doesn´t understand Star Wars or Netflix doesn´t understand the Witcher. Or maybe they do understand it but just don´t like it and want to make something different and just want the name for the associated consumer base.
When people say "respect the source" that often means "the source is good" rather than "do a 1:1 adaptation". I´m guessing comic book readers think of very specific arcs when they think about any given hero and compare against that not because they want a 1:1 adaptation but rather because that´s what define the characters for them. This or that good story is the reason this person love Batman or Spiderman or Superman or Wonder Woman.
That said success is not always related to quality... some times it´s marketing, some times is just giving the audience what they want. When you deny them what they want they feel cheated. People probably don´t feel like paying to see a wimpy Superman get his ass constantly handed to him or to be dissed regardless of how well he made.
