I have flown with several first officers in the past few years who could not locate a lat/long on a chart.
I had a first officer on a simulator PC checkride within the last few years who could not wrap his head around the concept of flying a raw data approach, or manually tuning and flying an approach. While "on fire" with vectors to a runway, we were told there were problems reported with the approach. I told the F/O to be ready with the parallel, and sure enough, we were flown through the localizer, told it was down, and cleared the parallel. Minimums were the same. Prebriefed. Inbound course the same. Charts were up; all he had to do was manually tune, and even that was prepared...but couldn't get past putting it in the box. He couldn't get it in the box, and we were inside the marker, landing, before he gave up. So focused on that magenta line.
One F/O so green that on the morning of his first live trip, he glanced at the low overcast and whistled, and said, "Wow, this is just like the simulator." Ya think?
I observed a OE candidate a few years ago who put in just shy of 200 hours OE. The operator refused to terminate the individual (again). The person had failed the type ride twice, I believe, was sent home, brought back and put through again, just passed, and sent to OE. I met with several check airmen who expressed frustration with the individual, but who were unwilling to be the bad guy and pull the plug. Eventually, the individual had just under 200 hours of OE before being let go. I observed some of the training, and saw a pilot who couldn't talk on the radio, fly a heading, hold an altitude, and was always full scale deflection on each approach. I examined the individuals resume and it's falsification was immediately clear. I had that discussion with each of the check airmen, who said that was their impression, but they'd been told to get the individual through training. It certainly wasn't for lack of trying when that person was released.
I don't know what the PRIA status was or might have revealed, because I wasn't part of that end at the time, but I can't see how anyone could be anything but willfully deaf, dumb, and blind, to miss it, and certainly the next operators, too. I was privy to a later checkride by the same individual, which was worse by some order of magnitude, than the previous observations, and that ain't easy to do.
Most of us are average joes, and smattered through the business there are the occasional aces of the proverbial base...but counterpoint to those, there are certainly some who seem to continually slip through the cracks, and there's always someone out there willing to hire them. It truly boggles the mind.