Isn't this what MUDs are? I tried a few in the early days of the internet and even back then they were like much bigger and more dynamic versions of text adventures of the 80s. For me I bounced off the idea that I had to role-play with other humans - I thought it was far more interesting to chat with other humans about real-world topics - but if you are looking for a large, text-based role-play experience then it's probably worth trying out a few. There might even be some that can be soloed these days, there are so many.
I think the challenge of trying to make an "endless" game using an LLM is the same challenge that all procgen games face - they are boring for people who are seeking a well-paced narrative. There are players who enjoy the mechanics of looting/crafting/trading/etc who will gladly play games where the story is incidental or emergent, but if you're specifically looking for something with a bit more narrative depth, I'm not sure procgen will ever work. Even if there is a system that tries to project coherent storylines onto the generated world, you still need the player to do things that fit into a storyline (and not break the world in such a way that it undermines the storyline!), otherwise the pacing will be off. But if the system forces the player into a storyline, then it breaks the illusion that the world was ever truly open. So you can't have it both ways - either there is a narrative arc that the player submits to, or the player is building their own narrative inside a sandbox.
AAA games try to have it both ways, of course, but it's always pretty clear when you are walking through procgen locations and leafing through stacks of irrelevant lore vs when you are playing a bespoke storyline mission that meaningfully progresses the state of the world.
What I wanted in MUDs was a simple editor to allow people with little technical skill a means to create a world—or extend an existing one. And then I wanted a way to join MUDs together—like if you leave a forest by a certain path you are, unbeknownst to you, rerouted to a different MUD that picks up where the forest left off.
In this way I imagined in time a world larger and richer than any that had come before it—where you could really just keep going, keep playing, never see all of it.
> chat with other humans about real-world topics
You can do this with regard to a MUD too, but typically out of character and not every MUD would allow OOC chatting within the game world, as that is disruptive to those players who seek immersion.
It seems to me as if you may not have found a good roleplaying MUD back when you played MUDs. You may be missing out on that experience. I retired from playing MUDs about 11 years ago permanently, but the in-world roleplay was the only thing that was interesting to me since it was the creation of a unique storyline potentially involving many other playercharacters.
MUDs are a low-tech version of what I'm describing. It relies on other people being available and generally leverages the usual tropes with repetitive killing-based gameplay.
LLMs are limited today, but one day they may be able to provide the well-paced narrative you're talking about. The LLM would be a skilled fiction writer that would introduce interesting events as I explore the world.
If I decide to go to a bar and talk to random strangers, it could give me interesting life stories to listen without any action. But, suddenly, a mysterious man walks in, gives me a sealed envelope and departs without saying a word... What is in the envelope?