Guess it's all just perspective! I think a family of ordinary people on an island full of dinosaurs can be acceptably "stupid." I mean, it's easy to hate the scene where Amanda screams for like 20 seconds when the skeleton drops, but, she would. At the very least I didn't find that stuff unrealistic. Now, a middle-aged man, who is also a paleontologist, running out of a hiding spot because a snake crawled into his vest, when the alternative is a Tyrannosaurs Rex, is both ignorantly and intellectually offensive. It's like, whatever "dumb" moments I can think of in the third one, there are one or more things in the second one that are arguably worse.
It's examples like this that separate the two sequels for me. The second one had Spielberg's expertise, but at the same time he was clearly about as into it as Koepp was writing the script, and Joe Johnston was actually thrilled to work on the next one as he wanted to do the second as well. I don't think Johnston is as talented as Spielberg, obviously, but he's still a fine director that at least brought some energy and charm to it. The second movie is about as charming as a stagnant pond. I like for some play in these movies. The original had scenes like the sick Triceratops, feeding the Brach, Tim pestering Grant, and so on.
I'm not saying the third movie was full of that, but it had some moments like Eric closing the hatch as the compies pass by with very whimsical music from Don Davis, and I just appreciate how vibrantly the dinosaurs are portrayed in it as opposed to the second movie, where again everything is just so damn drab, ugly, and lifeless.
As far as Billy selling the eggs on the "black market," I'm willing to buy it at least within the context of a science fiction action film. They were obviously struggling with research funding and it's implied that Billy had a run-in with the Kirby's first, so he was probably thinking go find Eric and hopefully find something that could net them a lot of money in the process. Whether or not he could realistically find a way to sell them, who knows. It doesn't really matter because it never quite gets there.