Why do my players keep leaving?

Hi Reddit, I am a long running GM, and play weekly (online) ttRPG sessions with some of my friends. It however seems impossible to find additional players to join, and I can’t tell why. Did I do something wrong?

Let’s start by giving you all some additional context. I am foremost a worldbuilder, and I love to play expansive games in my own setting. I try my best to bring my world to life and put a big emphasis on role play. Naturally the system is relatively rules light, but allows for some complexity to add to realism and immersion. (The world is a no-magic pre-industrial setting)

When asking my two players that have stuck with me they seem to enjoy the freedom and like the narratives I present. They are perhaps a bit in the shy side, but otherwise fantastic players. But it doesn’t matter, new players join in for a session and are gone by next week.

I have tried to ask these new players for their input, but there isn’t much they have said. They seem to be a perfect fit, yet they don’t want to continue. So I’ve tried to look at myself if they have some problem with me as a GM, but those two players keep ensuring me I’m doing nothing wrong.

What do you think, why can’t I get a third long-time player?