You got it wrong. RSA-2048 is not vulnerable to QC even theoretically.
Now you're just talking nonsense. Shor's algorithm factorizes n-digit numbers on a theoretical QC in time O(n^2 * log n * log log n) [1]. Which can in theory factorize numbers of tens of thousands of digits.
This is correct only with ideal noiseless qubits and gates.
That's exactly what a "theoretical QC" is. Hence, your claim of "not vulnerable to QC even theoretically" being wrong.
Shor's algorithm with noiseless qubits and gates works in theory.
Shor's algorithm with noisy qubits and gates does not work in theory. It needs exponentially small noise.
Both in theory.
That's it.