Yep, there are people who are actually shocked that the original Silver Age Green Lantern was a white dude and not Jon Stewart and got mad that they "replaced Jon Stewart" in the GL movie!I think the problem is that many fans view these properties through the lens of in-universe canon rather than how they actually exist: i.e., corporate IPs.
There are multiple iterations and reiterations of Batman, for example, throughout various media properties. The DCAU, for example, didn't strictly adhere to the DC "canon," but it made innovations to the stories and characters that were so influential (e.g., Mr. Freeze's new origin story, Harlequin, Renee Montoya, Terry McGinnis, Mercy Graves, etc.) that they reverberated back into DC Comics, and some fans primarily know these stories through the lens of the DCAU rather than the actual comics.
I prefer that these characters, including He-Man, are reinvented through new media rather than strictly adhering to some mythical canon. It keeps these properties fresh, updated, and alive.
WHen a new continuity is done well it almost rewrites on the public consciousness. Alan Moore did a take on this when he took over Supreme for Rob Liefeld back in the late 90s and completely reinvented the character causing Liefeld's universe to "reboot" to reflect those changes in the character. The Timmverse was so well handled that even the comics set there were often the better comics from DC in the time period.
It's all based on your first exposure to a character or concept. Transformers for example, for me, was the OG G1 series. I was one of the "Trukk, not Munky" people but now I dig the Beast Wars designs and have quite a few but I know people who are die hard Unicron Trilogy and Prime Trilogy fans because that's what was on when they were the target audience.
I wasn't an FR fan until 3e. To me 3e is the best FR but I recognize that the OGB is the best published version and not just because it was first. It is the most accessible and well written. Some people it's 2e era. But it's that exposure. For new fans it's Sword Coast. For new 5e fans... it's not really any defined setting. It's just the game.