I think what's really at the core of this is whether crows would figure out such advances given sufficient evolutionary pressure to do so. One could reason that crows are smart enough to avoid most situations that would cause broken bones but if something forced them to adapt, would they for example evolve thicker, stronger bones. Or if their common predators disappeared, would that allow them to build more permanent communities where they had the spare time to learn about their environment enough to manipulate it?

Humans by and large, especially in less forgiving environments with harsh winters, are helpless without the ability to manipulate their environment seeing as they are hairless apes who without modern medicine could die from an infection from a mere scratch.

Basically, it's an apples-to-oranges comparison.

Why crows haven't invented stretchers to carry fellow crows to safety? Making a stretcher doesn't look more complicated than building a nest.

A crow can carry about 1.5 lbs in flight. A crow weighs at most 4.5 lbs. Let's assume a stretcher that can carry a crow by more than one crow to weigh another 1-2 lbs. At most, the total payload would be ~5 lbs which requires at least 4 crows. I don't think that kind of coordination is possible with that kind of turbulence in such close quarters.

So why bother?