But the one ability they all lack is the ability to understand concepts.
I understood plenty when I was 3. I was learning to read when I was 3 -- by definition, I couldn't do that if I couldn't understand what I was reading. Your assumptions about intelligence are profoundly misinformed and profoundly wrong. You should try reading up on the subject rather than just assuming you're right.
The really important part of intelligence isn't just understanding concepts. It's understanding that you can be wrong and have incomplete knowledge. Accepting that is the only way you can open your mind to learning more.