This is how I would have plotted Generations.
The Enterprise (the real one) encounters a space phenomenon thing that knocks them about and makes them fall through a time warp thing into the future. There, they find the Enterprise D drifting and powerless. Boarding it, Kirk meets Picard and learns the following from him: “A renegade Klingon admiral is intent on attacking Earth and triggering a new war. We were the only ship in a position to intercept, but we ran into a space phenomenon thing that knocked out our power.”
“Klingon bastards” says Kirk (Worf is off on DS-9, so he can say that.) Then Kirk lends them Scotty, who moans about how stupidly over-designed the D is and it’s no wonder the phenomenon thing knocked them out when the real Enterprise rode through it, and then fixes the Enterprise D.
Together, they go to intercept the vastly superior Klingon force, where they give a good account of themselves, well, mainly Kirk using “old fashioned” tactics that work brilliantly because the Klingons have forgotten how to counter them. Picard flounders round indecisively wringing his hands and trying diplomacy, obviously.
But still, there’s no way to beat the odds, except Spock has worked out a way to use the energy of the space phenomenon thing to destroy the Klingons – it will require a ship to fly into the centre of it though, and surely be destroyed.
Kirk decides it must be them – it can’t be the D because that’s full of civilians and children (“what idiot thought that was a good idea?” ), besides, he knows only Sulu can successfully pilot them through it.
Plan executed, big explosion, Klingons wiped out, Earth saved. Picard orders a scan for the Enterprise, but there is no sign, not even debris. Were they annihilated, or is there a chance – just a small chance – that they were thrown elsewhere in time and still survive to continue their mission of exploration? We will never know… (Spoiler: yes they did, because it’s Kirk, he always snatches victory from the jaws of defeat.)