An idiotic achievement that shouldn't need achieving to begin with - if you want to force someone to rise to a do-or-die challenge, it's vital they're aware of that challenge. Breaking the Wheel and not telling anyone would not serve Eothas in his already moronic plan
Considering Eothas returned the reincarnation process to its natural chaotic state, and that the storms around Ukaizo stopped, people would eventually reach the island and get the gist of the situation. Conversations with Woedica imply that Watcher's pursuit is already part of mortals' rising to the challenge.
Deadfire's "god of wisdom" is a monstrously dangerous imbecile
He is not a god of wisdom. Look at this description from Deadfire encyclopedia:
Eothas is the god of light,
redemption, hope, and rebirth. Priests of Eothas are honest and kind in their dealings,
condemning all expressions of cruelty and
falsehood. Gaun is an aspect of Eothas that emphasizes the
natural ending of mortal life. Commonly represented as a farmer carrying a lantern and sickle, Gaun is a figure of cyclical death as
opposed to Rymrgand’s entropic one or Berath’s cold inevitability. The sickle he carries,
reaps what is sowed in life, and the lantern guides the deceased through
death and rebirth. It is believed that Gaun, instead of Berath’s avatars, visits those who
embrace death with acceptance.
Consider that his portfolio is universal, for mortals and gods alike. Are not his actions perfectly in line with it?
and Durance was right to blow him to smithereens in the first game's backstory.
And yet we see that a god cannot be killed with a big bomb, however cool that sounds.
Deadfire's main throughline is Eothas breaking the Wheel and the PC plays no part in the unfolding of those events, nor indeed could they in any capacity. With or without the protagonist's involvement, the exposition for a hypothetical sequel is identical, Eothas manifested as giant rock, waded through the ocean, and broke the recycle bin. The player is presented with no agency in that course of events, nor even the prospect of agency, and anything they could affect is purely peripheral.
Not every story is a hero's journey, and stories have layers. The Watcher has personal stakes - the souls of his people are imprisoned, part of his soul is taken, he is brought back from the dead on the condition of following Eothas - take your pick, roleplay.
At no point during the journey he is tasked with destroying Eothas - it is presumed to be impossible, even for gods themselves (see Wordica, Abydon, the Godhammer). You can stop him temporarily with a titan (yes, DLC) and it unfolds exactly like you described with cannons - he crashes into the Wheel. At least it's more dignified than galleon cannons.
At multiple points throughout the games you see that you can't skillcheck change a god's mind either. They are more preprogrammed machines than Greek gods, however man-like their behavior is.
On a higher layer the story is about the world itself, the nature of mortal and divine in a world with natural reincarnation, and the
relationship between both. If you reframe both games in this way, you can see them as acts 1 and 2 in a traditional story structure.
Game 1 is introduction to the
relationship and call to adventure (Woedica vs Eothas using mortals). Game 2 ends in the lowest point - the axis of the
relationship is broken - the gods will presumably cease to exist without the Wheel, while the mortals will be left alone in chaos. So, yes, the exposition for Game 3 is identical - it is Act 3 and you can't start it with the Wheel intact.
Roping factions in? They help you get to Ukaizo.
Do they? I know the game
pretends that's the case, but the way I recall it, all they do is sail with you through a big storm. Which you can also do on your own. Big whoop.
Each faction gives you the means to reach Ukaizo - teleport through the storms, go underwater, calm the storms or sail the ghost ship. You can fit your ship with an ultimate upgrade to go through alone if you wish.
Thinking about all this, Dune comes to mind. Paul is the protagonist, we explore the world largely through him. Despite being in the center of the events, he has little agency in the overall story (although for different reasons) and he himself knows it. It doesn't make the story less interesting, because the story is not about Paul in the end. It also doesn't make Paul's adventures less exciting.