the deeply unsatisfying thing about Jonah's arc is that he, out of all characters, gets relegated to the position of plot device. his agency in causing the apocalypse is completely ignored in favour of feeding into Jon's guilt and sense of responsibility; and since we, the audience, and even the characters themselves, know that it was Jonah who ultimately planned the Ritual, it comes off as rather forced. heaping the blame onto Jon is not only an unfairness to him, but to Jonah himself — the narrative in season 5 utterly fails to acknowledge that Jonah Magnus has been the driving force behind the development of the main character and of the very plot of the show. the Web may have been setting the orchestra in place, but Jonah was very much the conductor.
what little insight we gain into who Jonah was as a person is conveyed through other characters' perceptions of him — which would be interesting on a metatextual level if it had been intentional, in which case I believe the creators would have at the very least given us the protagonist's perspective on the man who shaped him. instead, Jon in season 5 seems remarkably indifferent to Jonah, and seems content to take full responsibility for the fate of the world; which, again, might have been an interesting thing to explore as a character trait, and not as a narrative truth. but I digress.
Jonah himself is a man who is fundamentally so afraid, so utterly terrified of becoming a victim he sacrifices the entire world for a chance at keeping himself safe from fear. he knows someone is bound to figure out the truth of the Rituals and eventually perform a successful one, and he wants, nay, needs to make sure he gets there first. we see him sacrifice every single one of his human connections over several lifetimes for the sake of achieving his goal (it's no coincidence that the non-Eye avatars with closest relations to the Institute are the Lukases; Jonah's terror of powerlessness has led him to viewing every one of his friends and colleagues as sacrificial pawns. it's an awfully Lonely place to be). he knows the world is hurtling towards a balance of stark duality, and seeks to place himself above it. there is so much about him that could have been elaborated on in ways that would have advanced the story.
but even if you don't particularly care for Jonah as a character (to each their own, I suppose), there is no denying his importance to the character of Jon. he made the protagonist. it's unthinkable that Jon would have no feelings towards Jonah other than a vendetta that, even with all the stakes laid out, still comes across as superficial. yet throughout all of s5, there is little to no emotional engagement with the character of Jonah on Jon's part. even Helen is afforded more emotional significance than Jonah, which makes no sense at all.
ugh. i was so convinced jon's refusal to think much about jonah was like, actually a character/plot thing being set up? the fact that he says "oh darn. i can't See jonah. better just not try again or think about him or my feelings about him and the whole situation or what i will do when i get there. what a shame. can't be helped"
basira even calls him on it!! when he says he can't see jonah she says "how convenient"!!! i dont think it was an intentional comment on jon's avoidance as much as "oh cool, nothing USEFUL from the eye, AS USUAL." but she really called attention to that interesting behavior!!! yeah, jon, sure is convenient you can't see jonah and therefore can brush aside any thoughts and feelings you might have on that front. why dwell on it if you have no information to go off? don't think about it. don't worry. don't confront or process anything.
i would have bet you anything that jon's "i won't hesitate" was a very obvious but beautiful setup for Jon, In Fact, Hesitating. the entire series jonah has been able to bend jon's ear, no matter how much jon hates him and is determined to resist at any given point, with the offer of exactly the right information.
it could even have been a final subversion of that dynamic with jon finally refusing to give in to jonah's tricks! i'd have loved that! i'd have loved jon to kill jonah with his own hands and finally get some catharsis not just for tim and gertrude and sasha, but for himself, for the first and only time allowing himself to center himself and his own grief. or, failing that, a moment of examination of jon's inability to do so.
in the end we had our showdown with the big bad, the man at fault for all of this, and got no proper exploration of the most pivotal relationship in the show (plotwise if nothing else). the orchestrator of the entire series is treated like an afterthought, and it is a crying goddamn shame.