Horrible screenplay.
They tried to adapt too much of the novel*, which made the plot convoluted and made individual points out-of-place (if you hadn't read the book, how insanely ridiculous would that scene about the egg shells and frog DNA be? it would seem to be inserted out of nowhere).
The acting and directing weren't terrible, but couldn't overcome the writing. And they weren't great, either. Laura Dern overacted, Sam Neill underacted, and Jeff Goldblum was... well, just another Jeff Goldblum clone. I know he has acting chops, so why do directors insist on turning all of his characters into the same person?
Oh, and speaking of Laura Dern, her character vacillated between smart protagonist and idiot damsel in distress like flipping a coin. That wasn't her fault. More bad writing, and directing mistakes, too. But then, love him or hate him (and I do love him), Spielberg has always had a love affair with cliche.
The special effects and music were wonderful. It certainly wasn't all bad.
goat
* Crichton was involved, so I wonder if that wasn't partially his fault. Novelists sometimes hate it when movies leave out parts of their books, without understanding that, for the movie to tell the entire story, it would have to be 8 hours long.