Welcome to obscurity.
When I was young, before there was steampunk and even before there was cyberpunk, there were fantasy novels and I read them them. I gobbled them up. I threw myself into the stories and didn't come out until I went off to college. Those were good years. Books were real books. Villains were real villains. And psychic thread fighting dragons were REAL psychic thread fighting dragons. Now when I look at the books labeled "fantasy", I see nothing that resembles fantasy at all. Can you even call a romance with a vampire a fantasy? I don't think so. So how did all those books get there on the top seller list?
I'm sorry, ELITE CABALS.
Or maybe, just maybe, those books made it up the best seller list because tastes change.
Take a look at Goodreads, finding their list of top fantasy novels by decade. You will see radical changes every ten years. Rarely do you see a name stretch across two decades. They may have been fantasic writers, but their names drop off the list. How could that happen to fantasic writers? Tastes change. Markets change. New generations come along and buy different books. Publishers, being the smart, profit-motivated companies that they are, chase the money. That means that the type of fantasy and science fiction that we expect to see when we go to the bookstore fades away in favor of someone else's fantasy and science fiction.
Now you know non-straight white males feel when they go into book shops and don't find anything catering to them. You know how they feel when they look at media. You know how they feel when they can't find anything that speaks to their own experience. The only difference is that you were once the target audience, so for you, it feels like something was taken away. I know. That's how I feel. I feel that way about fantasy, SF, music, TV, and all other sorts of media. I am no longer the favored child. Neither are you.
So you're screwed when it comes to your favorite media, right? Wrong.
There's decades of back material that still available. All of that material should still appeal to you. Books don't go bad. Yay, you get to win again and gain as you find series that you didn't know existed.
There's an indie market that feeds smaller markets, just like you. Finding what you want may be a chore, but I'm sure that your type of book is out there. Lack of seeing material doesn't mean it's not there.
There's all sort of other new stuff that you haven't tried. Go for it. You can't find a new love is you don't go dating. Other genres are full of fun. Histories are arguably better fantasy books than fantasy being both weirder and truer.
And finally, I miss being the center of attention, too. Those people in arthritis commercials are starting to look all too close to my own age. Pretty soon, I'm going to start looking at commercials for life insurance. Sometimes being the target demographic sucks.
Is it possible to turn the clock back? Sure, we can. That's called a revival. That happens when enough people get interested in a work. We saw a Lord of the Rings revival due to the films. We'll see another Star Wars revival when the next film comes out. Those revivals were easy to foresee. Other revivals? Those aren't so easy to predict. I'm still waiting for the Banana Splits revival.