Is slow burn fantasy even a thing anymore?

I'm in my 30s, and when I was growing up my dad got me interested in reading by reading his fantasy books out loud. This was David Eddings, Brian Jacques, Tolkien, Anne Rice, Terry Goodkind, etc. I used to love getting lost in those worlds and quickly picked up reading them myself. I felt like there was a lot more worldbuilding and a "slow burn" up to fantasy/adventure instead of immediately being slapped in the face with it.

I recently posted the first chapter of my fantasy story for feedback (on Facebook) and it got ripped apart by people who wanted, in my opinion, kind of cliche fantasy workings immediately. Like within the first few sentences. They wanted something with magic to happen, or some kind of creature or fantasy species to appear, and action right off the bat.

I work as an editor for mostly romance authors, so I know that these days the market loves immediate gratification in a lot of cases. To be honest, a lot of the modern-day fantasy I've tried to read is unappealing to me because it does the same: launches me into a cliche situation that is unsurprising and then tears off through a story with little worldbuilding or character development.

Is there still a place in fantasy for an old-school kind of story? I really wanted mine to be more of a mystery, with a subtle buildup to the magic and adventure. By "subtle," I mean that the magic appears in chapter 3; it's hinted at in chapter 1, but the character doesn't know it exists. Instead, I focused more on setting the world up: medieval-esque, with a forest that people are suddenly afraid of.

The feedback I got was disheartening, but I don't know if it's just the subset of people I asked. To be honest, a lot of them are focused on self-publishing with the intent to make money quick. That's not my intent. I just want to write a good story with a solid adventure that people can get lost in.

Any advice/similar experiences? Any modern-day books I should check out, or advice based on popular fantasy you've read? I really don't want to put this story down, but I'm feeling low after how it got torn apart for being too slow in the first chapter.

(Just a note: feedback also noted that the writing itself was solid, no mistakes/odd or awkward wording, etc. Just a lot of complaints that there wasn't immediate action.)