"Mr. Data, lay in a course for the 24th century. I suspect our future is there waiting for us."
"Course laid in, sir."
"Make it so."
Because they figured out how the Borg jumped through time.
And considering how many means of time travel there are, from the Borg's temporal whatever to the chrono deflector for the Klingons in "Endgame" (VOY), it kinda makes the old slingshot rather redundant.
But yeah, agree with the OP - would have been far more stylish to use the slingshot back. But tbh, this episode was great, a minor quirk like that is still a very minor quirk.
A minor quirk is writing that Scotty knows anything about "Transwarp Transporter Technology".... well maybe in the Abrams-Verse that might be true after timetravel Spock introduced him to the idea.... *cringe*...
putting a Flux Compensator on my ship... now that is a pretty big quirk in the storytelling i'd say.