The modern world and classical antiquity may have different relationships between science and engineering.

Perhaps the engineering achievements of antiquity were simple enough to be created empirically, without being backed by a scientific theory. You could build an aqueduct without mathematical physical theories, so you did, and science regressing (or not existing in the first place) didn't hold back engineering much.

But today engineering is creating greatly more complex things that are impossible without a formal scientific theory backing them. You can't make a transistor or engineer bacteria to make insulin without a lot of science. So today engineering is bounded by scientific progress.

Even in the second scenario, I think it's likely that a lot of things which can already be understood scientifically have not yet been done by engineers, so engineering could progress for a while in certain fields after science stopped.