Guinan tells Picard he can go “anywhere, anytime”...
And he immediately says he wants to go back to the planet right before Soren launched the sun-destroying rocket.
He can anywhere and anytime and change the timeline to stop the bad guy from destroying a star and killing a prewarp civilization. He could go back to when they first met Soren and keep him from destroying the Amargossa Observatory and kidnapping Geordi, or maybe even a few days earlier to save his family from dying in a fire first, but no. He decides to go back to when there’s like 10 minutes before the bad guy wins.
Then, he says he can’t stop Soren on his own and asks Nexus-Guinan to come too and help. Nexus-Guinan says she can’t actually leave, but if Picard needs someone to help him hold Soren down and shut off the rocket, who better than the most famous Starfleet captain of all time?
So now we have a massive plot hole about where and when Picard chooses to stop Soren and not a plot hole exactly about why Kirk comes back with him, but inexplicable. Kirk is a famous starship captain who’s famous for being a starship captain and Picard had him come be random hired muscle.
Then Kirk dies and rather than bringing his body back, Picard just buried him out in the open under a pile of rocks. Not a plot hole but an inexplicable moment.