People aren't freaking out over this signing because scheme matters. The only position the Steelers can put him in is the Mike position in a 3-4, the very same one he's been hot garbage at. Watt has the Will locked down, and Highsmith is the Sam, and the Sam wouldn't be a good spot for him either because he hasn't been capable of covering anyone for two years now.
Anybody who thinks LBer coverage of TE's will be downgraded by adding Jack apparently does not watch Steelers games. First, Steelers ILBers have not been good covering TE's. Not good at all. Second, the bigger problem has been that Steelers ILBers have been absolutely terrible the past two years at STOPPING THE RUN, a much more crucial role for them in this defense.