I have also had this theory! And I think it's interesting how it fits into with the Big Bads of each season arc. https://twitter.com/VeraRaeArt/status/1198387957666918411

Denial + Corruption: Jon denies the veracity of the statements, he denies how they're affecting him, he denies Martin's competence (since Martin believes the statements) and he denies that Jane is anything other than an unfortunate woman with a gross parasite.

The Corruption spreads and festers when it's not kept in check. Every visible mushroom is just the fruiting body of a larger, more pervasive fungus; every ant is a scout for a whole anthill. Jon's denial lets so many things fester -- and nearly got them all killed.

Anger + Beholding: while Not!Sasha was lurking in the background this whole season, arguably the real big bad is the Eye, and Jon realizing that it's claimed him. He's angry and scared and he channels that into wanting to know everything, because knowledge is power...

...or at least the illusion of control. Ironically, it's "blind" anger that leads Jon further down the path of the Eye, because he's so absorbed in his own feelings that he loses compassion for the people he's stalking.

Bargaining + Stranger: Jon spends the seasons trying to understand how all this avatar stuff works, and also to what extent he himself is already a monster. Pitting him against the Stranger when he's already alienated from his sense of self is just real on the nose.

Jon's a stranger to himself and everyone around him, and the half-season quest for a plan to stop the Circus is the ultimate form of bargaining: If I do x, y, z, then I can banish literal and metaphorical Unknowing and be myself again.

And of course, in season 4 is very, very literally about the Lonely and suicidal depression. Jon admits it after he gets Daisy from the Buried; Martin admits it when refuses to kill Jonah; Melanie, Basira and Daisy all face their own pain in near-isolation from the rest.

We get our hope spots: Jon and Martin escape from Peter, Melanie escapes the Institute. But the Lonely pairs with Depression so well because depression, even in a group, is isolating. "A room in hell with your name on the door."

So which entity pairs best with Acceptance, if that completes the cycle? The End would be a fitting one -- even mundane death is inevitable, and I doubt we're going to get a resolution to the story that doesn't involve a body count.

The Web also seems like a likely end boss, given how prominent she was in S4. And I think Annabelle's statement fits interestingly in the framework of Acceptance: free will is an illusion because we can't know what's pulling our strings, so why worry?

Jon's final arc might be turning that around: if we can't know what's influencing us then it might as well not exist. If it looks like free will then we might as well behave like it is, and accept responsibility for our choices rather than blaming a hazy outside power.

He's kinda on his way to this: he chooses to trust his team despite Eye-induced paranoia. Saving Melanie and Daisy and Martin were all right choices in the moment, even though they also pushed him towards feeding (and doing a murder) and also the apocalypse.

Elias's "choices" monologue was, in hindsight, hella manipulative BS. So a S5 resolution that subverts that would be cool: we make the best choices we can with the knowledge we have, and when we know better, we should choose better.