I think you know that’s a cliche in some circles and my intention is not to try call you on that without reason, but to ask about it practically speaking.
Would you agree that it seems for many disciplines, whether its cs or physics, the power of the statement “it’s solved theoretically” relates to the scope of the problem?
For example, if someone came up with a strong argument or proof that raises the upper bound of performance for a specific algorithm, I could be convinced to start celebrating right away, and would think nothing of the implementation being passed off to a student as a mere formality.
However, the scope doesn’t have to increase much before a formal proof, or even a conclusive argument, become impossible to make in a way that’s completely convincing.
It’s not a knock against either theory or engineering, it’s a simple matter of our inability to model or predict things accurately beyond a certain complexity.
I only wish I could explain this well to lay people, like if a friend asks me, “after over half a century of writing code why cant even the greatest software companies in the world reliably predict how long it takes to ship software?”
Maybe next time I’ll tell them, “it’s the same reason we need database reference implementations”. It will just add more confusion, but at least I can spit out some kind of answer.