Not at all. Yuji Itadori's story doesn't end with his execution in the manga. There are many developments and challenges he faces, but execution isn't one of them.
Yuji Itadori survives till the end. The manga doesn't have his death as the final outcome. The story might have thrown challenges at him, but he manages to overcome them and remain alive.
Yuji is still kicking in the JJK manga. The plot has thrown many challenges his way, but death hasn't claimed him yet. Who knows what the future holds though!
In a fanfiction, the plot could revolve around Yuji and Nobara being sent to a different dimension. In this dimension, the rules of jujutsu are different. They have to adapt quickly and find a way back home. During their time there, they meet strange versions of their friends and enemies. They must use their wits and powers to survive and figure out how to return to their own world. This experience changes their relationship and makes them stronger as a team.
One idea could be a story where Yuji and Nobara go on a special mission together in an unknown location filled with new types of curses. They have to rely on each other's strengths more than ever.
Itadori did indeed die in the manga. His death had a significant impact on the story and the other characters. It was a turning point that led to many new developments in the plot.
Itadori is quite powerful in the manga. His strength lies not only in his physical abilities but also in his determination and the unique powers he acquires along the way. He's able to face off against formidable opponents and come out on top more often than not.