Yeah, we're unlikely to randomly create a highly intelligent machine. If you saw someone trying to create new chemical compounds, or a computer science student writing a video game AI, or a child randomly assembling blocks and stick - it would be absurd to worry that they would accidentally create some kind of intelligence.
What would make your belief more reasonable though is if you started to see evidence that people were on a path to creating intelligence. This evidence should make you think that what people were doing actually has a potential of getting to intelligence, and as that evidence builds so should your concern.
To go back to the idea of a child randomly assembling blocks and sticks - imagine if the child's creation started to talk incoherently. That would be pretty surprising. Then the creation starts to talk in grammatically correct but meaningless sentences. Then the creation starts to say things that are semantically meaningful but often out of context. Then the stuff almost always makes sense in context but it's not really novel. Now, it's saying novel creative stuff, but it's not always factually accurate. Is the correct intellectual posture - "Well, no worries, this creation is sometimes wrong. I'm certain what the child is building will never become really intelligent." I don't think that's a good stance to take.
What would make your belief more reasonable though is if you started to see evidence that people were on a path to creating intelligence. This evidence should make you think that what people were doing actually has a potential of getting to intelligence, and as that evidence builds so should your concern.
To go back to the idea of a child randomly assembling blocks and sticks - imagine if the child's creation started to talk incoherently. That would be pretty surprising. Then the creation starts to talk in grammatically correct but meaningless sentences. Then the creation starts to say things that are semantically meaningful but often out of context. Then the stuff almost always makes sense in context but it's not really novel. Now, it's saying novel creative stuff, but it's not always factually accurate. Is the correct intellectual posture - "Well, no worries, this creation is sometimes wrong. I'm certain what the child is building will never become really intelligent." I don't think that's a good stance to take.