I don't think the model is worthless. But there also going to be many real world scenarios where they aren't good enough.
It's like doing physics where you assume perfectly uniform spherical objects in a vacuum. It isn't worthless just because that isn't how the real world works, but depending on the circumstance it can also give you incorrect results, and sometimes even be way off.
It's like doing physics where you assume perfectly uniform spherical objects in a vacuum. It isn't worthless just because that isn't how the real world works, but depending on the circumstance it can also give you incorrect results, and sometimes even be way off.