There isn’t a simple evolutionary definition of “fish”, not the same way there is for, say, mammals. If you found the common ancestor of everything we call a mammal and said “everything descended from this one is also a mammal”, you’d be correct. If you did that for everything we call fish, every animal in the world would be a fish. Also, we decided which animals were fish mostly on vibes, so without a clear definition you can pedantically argue that everything is a fish including mammals.

If nothing else, it seems reasonable to assume that a computer could run a program that does all the important things 1 neuron does, so from there it’s “just” a matter of scaling to human brain quantities of neurons and recreating enough of the training that evolution and childhood provide to humans. But that’s the insanely inefficient way to do it, like trying to invent a clockwork ox to pull your plow instead of a tractor. It’d be pretty surprising if we couldn’t find the tractor version of artificial intelligence before getting an actual digital brain patterned directly off of biology to do it.

It’s making mistakes and failing to think abstractly at levels previously only achieved by humans, so it’s only rational to expect it to take over the world in 5 years

That’s a decently rational response you’ve described, though. If you were really at immediate risk, you’d probably know it, especially with an alarm going off to get you looking for signs of danger. And it’s usually better to have a lazy, skeptical evacuation than a panicked stampede. Schools do fire drills to check the alarms, sure, but it’s also important to make them a routine thing that all the kids know how to handle.