People who complain when fanfic writers don’t do things exactly like canon have a fundamental misunderstanding of what fanfiction is/should be.
Fanfiction is not a regurgitation of canon topics/concepts; it’s a dialogue that exists with and sometimes against canon. It explores concepts and topics the source material either ignored or had no interest in exploring in the first place. Fanfiction was born because canon stories didn’t tell the kind of stories fans wanted to see (What if Spock and Kirk were a couple? What if the cast of Star Trek were explorers during the 15th Century? What would it take for these two enemy characters to fall in love?)
To say that fanfiction is beholden to canon is just bullshit and to hound writers for not slavishly worshiping the source material is not only rude, it’s against the spirit of fanfiction. Great fanfiction takes canon into account but alters it in light of the story being told. Characters change given new/differing situations. Relationships evolve because the author is exploring new ground/circumstances. If nothing changes or if no new insights are revealed because of the story and everything is exactly like the source material then what’s the point of reading the story in the first place.
We should be looking inside for answers, not digging in the dirt to find ancient texts that supply a back story. The future is meant for those who are willing to let go of the worst parts of the past. When you cannot take two steps without turning around to inspect your footsteps, you are getting nowhere fast.