It's somewhat speculative (because no one ever tells you the reason for dropping your application or not contacting you in the first place) but the impression I have, echoed by what many others seem to be saying, is that the process has shifted greatly from "Is this a strong, reliable, motivated person?" (with toolchain overlap being mostly gravy) to "Do they have 5-8 recent years of X, Y and Z?".

As if years of doing anything is a reliable predictor of anything, or can even be effectively measured.