It's the shows' job to set up frightening situations. I think the point of the thread is, why don't more of those situations turn into disasters? Because they need the show to keep going of course, and the stars to stay alive, and not have the basic situation (Federation) changed... But yes, after hundreds of episodes in different centuries, the Federation has had a charmed life, just squeaking by, presumably not just on the ship we see, but on lots of other ships encountering these things. Humanity etc could have been wiped out by any one of these crises.
I think of the Sheliak, and think of how many other groups out there must also be more powerful and have no patience whatsoever for us. Others may not have the Sheliak's legal fixation. That's all that saved any human from them, and what if they came our way? That seems more realistic, relatively speaking. They won't all be at our power level and no stronger, our size, with similar comprehensive skills and values.
I think of the Sheliak, and think of how many other groups out there must also be more powerful and have no patience whatsoever for us. Others may not have the Sheliak's legal fixation. That's all that saved any human from them, and what if they came our way? That seems more realistic, relatively speaking. They won't all be at our power level and no stronger, our size, with similar comprehensive skills and values.