DeBrincat was playing with a rookie 3rd line center most of this year (Pinto). Norris was injured and I don't remember any game where he was given a chance to play with Stützle from start to finish.
Any center in Detroit will be a big update to this, let it be Larkin or Kasper or someone else who could be signed in the future. He will be good for 35+ goals at least.
Also, DeBrincat is someone who brings a lot to the table: he is fast, has great hands, can hold a puck in the corner, can rush a puck from zone to zone and he can make plays happen by himself while not shying away from fights. He is gritty and feisty. Detroit is lacking these skills, especially with Bertuzzi gone.
If you get a chance to sign him without hurting yourself too much, you do so. DeBrincat has the potential to be a fan favorite within few games, he is a great fit to the Detroit type of hockey. He is basically a more skilled Bertuzzi without the injury-proneness and the off-the-ice-ineptitude.