There's a big difference between symmetric and public key cryptography when it comes to this sort of explainability.
Public key cryptography like RSA, Elliptic Curves and Lattices have elegant mathematical theories behind them. Learning those will teach you much about why things are the way they are and how the security boils down to well known hard problems.
Symmetric key cryptography like SHA2, SHA3 and AES don't have nearly as much theory behind them. It's a bit of a dark art where functions are designed to thwart known attacks. There is no foundation like a proof that shows breaking SHA2 is equivalent to prime factorization or anything like that.
This doesn't necessarily have to be the case, there is research in 'provable secure hash functions', but these tend to perform worse, and we value performance a lot in symmetric crypto.
And yet...it's because of that theory that public key crypto is known to be more vulnerable to quantum computing attacks. Quantum computers can't break modern symmetric crypto.
Indeed, understand-ability is a double-edged sword in cryptography. In general it's best to follow Kerckhoffs's principle and make sure you understand why it works, or risk that your adversary learns more than you do.
> Quantum computers can't break modern symmetric crypto.
Much like we don't have proofs that it is classically secure we also don't have proofs it is secure in a quantum setting. But absence of proof is not proof of absence. In fact we know that Grover's algorithm halves the strength of any hash function. In general you should assume that symmetric cryptography is easier to break on a quantum computer than on a classical one because they are strictly more powerful.
In case of RSA and Elliptic Curves, we known there are theoretical quantum algorithms that undermine the security. But for Lattice cryptography there are actually proofs that they remain secure in a quantum setting.
Public key cryptography like RSA, Elliptic Curves and Lattices have elegant mathematical theories behind them. Learning those will teach you much about why things are the way they are and how the security boils down to well known hard problems.
Symmetric key cryptography like SHA2, SHA3 and AES don't have nearly as much theory behind them. It's a bit of a dark art where functions are designed to thwart known attacks. There is no foundation like a proof that shows breaking SHA2 is equivalent to prime factorization or anything like that.
This doesn't necessarily have to be the case, there is research in 'provable secure hash functions', but these tend to perform worse, and we value performance a lot in symmetric crypto.