Let me vouch for that answer as a propulsion engineer.
There is nothing practical you can do to prevent a commercial engine from ingesting a bird that is determined to enter the intake. Any screen more robust than some flimsy chicken wire will produce unacceptable pressure losses in the incoming flow. Airlines depend on wringing every last bit of efficiency possible from their engines, and the performance hit from a FOD* screen that could stop a goose would be massive.
Military aircraft may have certain FOD avoidance measures built in. But these usually rely on being able to take advantage of a certain length of inlet duct to help separate foreign objects from the air stream. Commercial airliners don’t have embedded engines with long inlet ducts to work with a FOD rejection system. That’s because, again, they need all the efficiency they can get. And a near zero-length inlet on a pod-mounted engine is the best way to wring maximum performance from your jet.
They do use FOD screens in ground testing of engines. You may see a conical mesh cover put over the inlet of an engine on a thrust stand. But those are meant to stop the relatively casual ingestion of a stray bolt or pebble. They are not what you would need to withstand a 10-lb bird hitting the engine face at 200 mph. It’s like fencing equipment. The mesh face mask will help stop a foil from hitting you in the eye, but it won’t do anything to keep you from being shot in the face with a .45.
So, because there’s no practical way to keep a bird from getting in the turbomachinery, the best the engineers can do is design the engine to be as tolerant as possible of ingesting such material. When you consider how complicated turbine engines are, they’re doing a remarkable job if they can have any success at all. The fact that an engine can ever withstand a birdstrike and keep operating is amazing to me. But they’re not bulletproof, so sometimes you have what happened yesterday. And geese are pretty damned big…so yesterday’s accident was hardly surprising (if it happened they way everyone thinks).
*Foreign Object Damage