I've never understood why it was taken for granted by everyone involved in the production that the first TNG film had to be crossover with the original crew. If they didn't believe TNG could stand on its own on the big screen, they shouldn't have bothered with a movie in the first place.
From what I gathered from interviews, Berman and the TNG staff were reluctant to do it, but Paramount mandated it, which was bogus. The same audience who embraced TNG on TV are the ones who would go see the movie. By 1994, Trek was a juggernaut franchise with TNG and DS9 and Voyager on the way. Shoehorning in Kirk was misguided fear by the suits.
From what RDM and Braga said in interviews and commentary, they had a really hard time figuring out a way to bring Kirk and Picard together. That impacted being able to craft a decent story, so as a result, the entire movie is big patchwork.
Ironically, the meeting of Picard and Kirk is anti-climactic. As RedLetterMedia points out in their review, Picard first tries to get Guinan to come back with him to fight Soran. She says she's just an echo and can't leave, but there's someone else who might help. So Kirk is just a stand-in for Guinan.