I mean, I feel y'all forgetting how Shibuya ended. The Mahito final fight was utter bullshyt too dude overcame everything thrown at him with every asspull imaginable and then Kenjaku basically one panel'd him
So I wouldn't be shocked if we continue to get "yada yada I have the ultimate answer to your incredible power by having this thing no one knew existed". I truly hope Sukuna and Yuji's storyline is treated more carefully than that but at the end of the day this is a shounen manga we are talking about
Ehh, that's debatable. All dude said was "If you accompany me for up to one more year (probably), I will be very happy". Translating this type of shyt from Japanese is always very tricky. And we also shouldn't forget that these authors tend to say shyt and then pull back and say "I'm very sorry I didn't (insert promise or deadline)". I think the only one that really was true to her word was Gotouge with Demon Slayer.
IMO this was Gege's biggest mistake with this fight. I think Gege feels like Yuki was presented like a beast that was a legit threat to Kenjaku, who just got lucky with a last minute asspull/guess. But it didn't really read like that, I think most of the readers felt Yuki ended up being underwhelming, she was hyped (in the manga) and showed crazy powers, but Kenjaku never felt in real danger to most of us.
To be honest, I kinda hope this wasn't the end of Yuki and her and Tengen had one last trick up their sleeves. Her being a former star plasma vessel could lead to some fukkery...but at the same time, Gege has no issue killing characters and leave threads hanging because of it.