This is exactly the problem. "Able to learn new technologies, and pick the right one for the problem at hand", is virtually impossible for HR or a recruiting company to evaluate. If they're supposed to filter out the obviously unsuitable candidates so that the devs and tech managers only have to interview plausible candidates, then they will go with keywords, because that's something they can do.

In other words, we have a systemic problem. If everyone does what the current system incentivizes, we get the wrong result.