The problem is our fans' expectations of a full-back. He's nowhere near as bad as people make out - it's just that so many have absolutely no clue what they're talking about, but have their uninformed opinions consolidated in an echo chamber of like-minded know-nothings. So people think they're spot on about Aurier being this terrible player when the simple reality is that he isn't.
I used to think the same as this but in reality he makes one unforced error that leads to a chance almost every game. Its stunning the regularity with how it happens, he gets caught on the ball way too much and his attacking performance since the league restarted has been wasteful at best.