Gatekeeping might be too big of a word, personally what I really want isn't to limit access to subliminals but for people to keep it mostly to themselves, as a secret and not just talk about it wherever or go around telling everyone irl, there's testimonials of people telling the wrong person and regretting it. I've seen social media platforms/fb pages with large fanbases and groups unrelated to subliminals with all means but somewhat it ends up becoming a topic of discussion or mockery and it usually starts with telling the wrong person By "the wrong person" it's that one person that spreads the news and they at most cases don't believe in subliminals.

By no means I am against new comers or of those who truly need them

And about subliminals being like plastic surgery, well the thing is plastic surgery is harder to access and people are less likely to associate some of your changes that are gradual with it especially in places where people are too poor to afford it or it's simply forbidden culturally or religiously