They don't make stoppers big enough for holes that size
There's holes all through the movie.
1) Picard is always careful about not altering time lines throughout the series, but he has no trouble altering it in Generations. He goes back in time to prevent Soran from altering the path of the Nexus. Why is it ok this time?
2) Guinan tells Picard in the Nexus that he can go to any time he chooses (something like that) so why doesn't he just simply stop Soran at an earlier time period, instead of having to enlist Kirk's help right before the Nexus is about to hit the planet?
3) Now that I'm on a roll, the destruction of the Enterprise was a problem. The shield's frequencies displayed for all to see? That allowed the Klingon's to see the frequencies via Geordie's visor and therefore find a way to shoot through them. Weak, weak, weak. I worked on missile systems and secret info like frequencies is never displayed in the open, it's "coded" to prevent anyone that shouldn't know what they are to find out.
And so on.....