The OP seems to be assuming the abstractions in the over-engineered code are all clean. If that's the case, the abstractions really can be like partially-solved

The OP seems to be assuming the abstractions in the over-engineered code are all clean. If that's the case, the abstractions really can be like partially-solved portions of a jigsaw puzzle. It's a common, flawed conceit that you can get design clean abstractions up-front with pure engineering discipline/process, though.