I dated a stupid girl right after college. At first, I thought she was just intensely introverted.
Nope, she is truly stupid. She didn't understand what "multiply" means. She thought Africa was a country in Europe. When she heard "homophones", she said (and I quote) "They're the ones who hate the gays, right?". She didn't understand that she puts a liquid into her car for fuel; not literal gas. She was 22 years old (i.e., she met me) before someone explained to her that lightsabers aren't real.
She graduated high school by the skin of her teeth. Sometimes I think she worked harder to NOT work than she would've worked if she just APPLIED herself. She aimed low in life and barely attained that.
I just can't tolerate that. We got along well (how could we not?) but there's no there there. She would always be unable (and largely unwilling) to face life's challenges. I question her ability to manage finances in any way. I'm surprised her parents (whom she lived with) allowed her to have her own bank account, frankly. She simply doesn't have two IQ points to rub together.
To her credit, she legit a heart of gold. She wouldn't hurt a fly. She wouldn't even be mean to people when they were mean to her first. "I don't have to do anything. God will take care of them soon enough." She helped strangers who were down on their luck. She always had time to be charitable to the truly unfortunate in society. She made friends everywhere she went. She wasn't the deepest well on the farm. But she was a good person.
And she was also a complete idiot. This, I do affirm.
Disclaimer 1: True stupidity is rare. Don't believe the rants you see online. Those are written by people with above average intelligence as they gripe about people with below average intelligence. By definition, average intelligence is the most common. As authentic genius is rare, so too is genuine stupidity. Most people have met very few truly brilliant people. They're also met very few truly stupid people. It's just not likely to happen. You're more likely to meet someone with below average intelligence. But don't mistake that for stupidity.
Disclaimer 2: And be humble! You're not the smartest guy in the world. There's always someone smarter. So, don't lord your higher intelligence over others.