No villains in this movie
I thought it was really interesting that there were no mustache-twirling, straight up villains in this movie (except for the dinos, of course). The Kirbys were just scared, desperate parents, and the mercenaries they hired weren't really bad guys - they didn't even know about basically kidnapping Dr Grant. And Billy made a stupid, impulsive decision, but he clearly regretted it and was crushed by Grant's disappointment.
I just think it's unusual, because there's normally at least one selfishly motivated, immoral character in these actiony-type movies. I thought it made the characters more realistic, oddly enough.