"Genesis" is not the "Spock's Brain" of TNG; it's much worse than that. "Spock's Brain" is at least an entertaining implausible story with plenty of 60s style. "Genesis" is simply dumb for all of the reasons that Trekker4747 stated and more.
The moment that killed it for me? Crusher finds out that Worf has a venom sac, then proceeds to ask him to open his mouth while she's standing right in front of him. What did she think would happen?
The moment that killed it for me? Crusher finds out that Worf has a venom sac, then proceeds to ask him to open his mouth while she's standing right in front of him. What did she think would happen?

I really don't like the light, humourous ending, though, when you think of the implications of what all this has done to the crew. OTOH, it's such an outlandish episode that to address all that would have probably been too big an issue.