Shaw provides less on the BLOCKING end of scheme and will never be a producer on the defense... He is an over hyped player they have had year in and out. People just ignored that because hype of 30 tackles... but that is replaceable by multiple people.
It wasn't like all his tackles were great plays short pickups on the field, he isn't half the talent Brandon Ayenbejio was who should of been a player kept. Does anyone even recall the name of Joey LaRocque? He was a stand out special teams player of 08 who was cut going into 09 because they knew he was replaceable and not a legit linebacker.
Also since they don't have a legit FB other than Clark who hardly is while at Hback.. it's not a bad move to keep 4 RBs, that's normal. Bell looks like he'll be inactive but he made the 53 with his play. When your JUST a special teams player like Shaw and will contribute absolutely nothing else you have to make the active 45 list of players and he wasn't able to because the team wants to actually win not just stock fan favorites with contributions in area.