No. Getting a cut is hardly an injury. Big E isn't slamming people on their heads and necks and being unsafe. There's a difference between being unsafe and getting a boo-boo. Case closed.
I think it's kind of a dick thing to say (safely from behind your keyboard and not in the ring risking your life . . . which could be an assumption, for all I know you could be Jeff Hardy or some shit posting on Wrestlezone in between bumps of cocaine and swinging from trees booty butt naked in the redneck wilderness or some shit) getting busted wide open and needing stitches is a "boo-boo", considering the art of professional wrestling is to protect your opponent while still looking like you're fucking their shit up. I believe Bret Hart said something to the effect of, "if someone gets injured, someone did their job wrong"
That being said, to answer OP, the reason why Ryback gets shitted on is because people are constantly wondering why he isn't higher up on the card. And rightfully so, dude got demoted from the unstoppable force main eventing PPV's to midcard/jobber tag team with Curtis Axel, and became even
more entertaining (outside of the ring, i.e. in promos, on social media, his mannerisms on the way to the ring, coming out and circling the ring during other people's matches).
So people are wondering why he isn't higher on the card and featured more prominently on RAW in an era devoid of full time star power. And for some reason we as internet wrestling fans seem to think an account on an online wrestling forum grants us magical mind reading abilities and we know what Triple H and Vince McMahon are thinking, and due to his history of injuring people that's the first straw people grasp at.
In my opinion, it seems as if big muscular dudes in general have a tendency to be unsafe. Brock Lesnar, Big E, Goldberg, Ryback, etc. I feel like through training, they should be striving to get better and safer every chance they get.