No one is honestly expecting the local governments throughout the Pittsburgh metropolitan area to eliminate 150 bridges (or some other arbitrarily large number) by 2023... They expected the local governments (and the state and federal governments) to behave competently and never let it get to this point. The decline of Pittsburgh as an industrial hub started over half a century ago... They've had plenty of time to address things like this in that context.
The fact that keeping infrastructure safe is "political suicide" or "costs too much money" is essentially the entire problem - and it's a problem that is not at all unique to Pittsburgh.