Also being trapped wouldn't be all that big a deal, slingshot around the nearest star and then they're home.
There are always ways around that though - clearly temporal slingshots are not feasible for so many situations since they're simply not used outside of a few occasions shown on screen.
Granted Kirk seemed to have little difficulty completing them, but why wouldn't they be used by hostile forces to destroy an enemy before they had risen to power and so on?
If anyone is familiar with the Millennium
trilogy by the Reeves-Stevenses, they included a suitably convincing technobabbley explanation why the Defiant couldn't simply slingshot back to the 'present' after being thrown a couple of decades into the future.