If I were to guess, the missing building block is the ability to abstract - which is the ability to create a symbol to represent something. Concrete example of abstraction is seen in the axioms of lambda calculus. 1) ability to posit a variable, 2) ability to define a function using said variable, and 3) the ability to apply functions to things. Abstraction arises from a process in the brain which we have not understood yet and could be outside of computation as we know it per [1]
[1] https://www.amazon.com/Emperors-New-Mind-Concerning-Computer...