But we're not talking about ranking journals. We're talking about ranking authors. JIF if a reasonable metric for journals, the problem is that it's used to rate authors: what's the JIF of journals you publish in?

The metric presented here is much better for rating authors because it gives more of an author's peers an opportunity to vouch for him by citing his work, as opposed to only a small editorial board and review committee who decide if he gets into TopJournalX.

Adding a pagerank-style coefficient (increasing the weight of citations that come from well-cited papers) would make this metric even better for precisely the reason you state: papers exist in perpetuity. If I write a paper now but it is ignored for 50 years, then someone builds upon that to break ground in an entirely new field, then I deserve some indirect credit for that. The journal I published in does not.