Gaz retired with 35 assists in the EPL, Evra had 21 assists, Irwin and Phil Neville (yep Phil) had 25 assists, Shaw on the other hand has 7 assists. AWB (classic defensive FB) had 4 assists this season alone while Shaw produced 0 assists this season. AWB have in total 7 assists in 73 matches, a reasonable chunk of whom he got them with Palace (a team that barely ever leaves its own half of pitch). Shaw has 7 assists in 155 matches most of whom he played with Manchester United (ie an attacking team)
As Gaz once said the FB role has evolved in the last few years and what was good in the past is not good enough now. With wingers acting more like inside forwards, fbs are expected to be able to go forward and act like the traditional English winger while concurrently be able to defend like a regular FB would do. In fact there was one instance when Gaz even questioned whether he himself would be good enough to play with a current serious title contender team (which in my opinion is false modesty but anyway).
Shaw is not great defensively, he's not great attacking wise and he's injury prone. This squad has too non players ie players who just sit there and play despite barely having any strengths whatsoever. We're not talking about being WC here. I mean Gaz, Park, Butt, James, Smalling and Ole weren't WC but there were aspects in their game that made/makes them great or at least good. We're talking about players like Shaw, Lingard and Lindelof whom you could sit down for hours and you can barely come out with anything that justify why the feck are they wearing the red shirt.