It really depends on what we're talking about, because I feel the term 'gate keeping' gets misused a LOT.
I think an inherent misconception is that nostalgia is the main cause behind some of the uproar about newer shows/movies, especially those that are reboots or reimaginings of older content. While there may be some nostalgia involved, I guarantee it's an extremely small amount, because there's an insane amount of media that gets remade/updates/etc. across all spectrums (music, TV, movies, books, etc.)... and there's no backlash at all. Even in the cases of extreme departures, you don't always get the backlash. So what's the difference?
The main difference is how they are being remade and why. One big aspect is whether you are respecting what came before it, whether it's from the perspective of lore, messaging, etc. For a lot of the newer remakes, they are not just disrespecting and warping what came before it, they're burning it down and urinating on the viewer and telling them it's raining. If the creators of the new content actually enjoy what came before it and want to add onto it, it's easily shown, and no one makes a big fuss over it unless it's really bad (then everyone makes a fuss usually). However, we get producers talking about how their goal isn't to entertain people, but turn shows into a messaging platform for their own views. This is typically done by destroying everything they don't like about the previous content (by making massive fundamental changes that typically aren't in-line with anything the previous show was about). In the end, you get something with the same name as the old content, but it's nothing like the old content... and as of late, it tends to insult the old content and anyone who enjoyed it.
Putting the views aside, the storytelling and writing has been getting pretty bad, and it stands out when the aforementioned issue comes alongside it. If anything, it's nostalgia that blinds people to how bad the writing really is in the newer stuff, where the creators like to jingle the car keys in front of the viewers to try to distract them from the trash that the content really is. Marvel is a good recent example, where the character stories, universe, and even themes/messages from the movies are getting absolutely destroyed by the recent shows that they put out. Unfortunately, as is the case with Marvel, the degradation of writing and story can be at least partly blamed because of the aforementioned issues: messaging over entertainment. Even with massive budgets, Marvel (and other large companies) cannot put out a decently written product because all their focus is in the wrong place. While you still may get some push-back concerning messaging, a well-written and entertaining story actually eliminates most of said push-back.
Now this isn't to say there wasn't trash in the past... goodness, there was. However, the needs to preach and berate your viewers was pretty rare, and even if you were trying to promote a message the end-result could still have good writing and be entertaining. Unfortunately, media now is the result of a culture that doesn't believe in any fundamental truths, where anything from the past is problematic and should be erased or rewritten in a more 'acceptable' way. We're not at the pure dystopian levels of 1984, but a lot of the societal culture that Orwell described is showing up in our culture right now... and it's affecting a lot of the media people see today.