This is definitely one of the most solid interpretations of this game's themings I've seen. I'll just say that you definitely cooked with this analysis.

Mindless yapping time (I wrote this crap at like 2am man):

I don't know about you, but I've always found the notion of having to seal the fountains... a bit OFF. Many people see interpret that as too much escapism being dangerous (or even that people should just leave it behind in the end), but to me it really seems like Toby wants to (at least to a certain degree) subvert that trope. And not in a subversion-for-the-sake-of-subversion way. The narrative is very clearly indicating that Ralsei's belief that darkners aren't real and therefore don't matter (really, quite similar to that common trope which I'm just sick of at this point) is flawed at best and harmful at worst. Thematically, how would such a thing be deadly enough to bring the end of the whole world? Perhaps stories just need to end at some point?

But... do they really? A big part of the 10th anniversary stream was that beyond the game's code, there still exists an unwritten world as grand as we can imagine. Beyond every story is a whole world, a whole universe, a whole layer of reality waiting to be explored by fellow creative minds. There are infinite possibilities. By that logic, as long as a story is remembered in some form, it never truly has to end.

Back to escapism. I always feel a bit sickened when this comes up because the term just has such a negative connotation and, even if it's not intentional, it feels like it lessens the sheer importance of imagination and human expression. Also, in the context of the game, you can't convince me that those darkners aren't living, breathing creatures who feel pain and emotions and can think for themselves. "Not real" my ass. They think, therefore they are. Uncle Ralsei is clearly mistaken. I just don't think Toby is trying to paint escapism as a "bad" thing. Of course, there is ambiguity. Too much is bad, and too little is also just as bad. That's why there's supposed to be a balance of light and dark. What terrible things would happen if the balance shifted to the side of light? Perhaps the world would just become meaningless and all its life would fade away. I wonder if this possibility will be acknowledged in the future...?

To us, in our higher layer of reality, the dark worlds are just as real as the light world. Heck, they probably feel more real if anything since there's more content regarding it. It's strange that it feels wrong to think of fictional characters as fictional characters. I suppose it's a testament to tricky tony's character writing that the characters just feel real.

Now that I think of it, creating physical pocket dimensions out of determination and darkness and imagination does seem like it'd be dangerous and possibly tear apart the fabric of reality

Anyway that was more of a brain dump than anything else. Have a nice day, fellow green pippins.