Lawson was drafted for a specific role in a specific defense. He is replacing a highly productive (albeit inconsistent) player who did not fit into that specific defense. If this specific defense does not perform this year, there is a high likelihood that it will be scrapped and a new coaching staff will be ushered in, potentially rendering Lawson a poor fit.
I've said it before, it continues to be my view that the Bills should've traded down from 19. We know Dallas was interested, other teams may have made offers as well. If you're going to take a medical risk, do it in Round 2, on a player with a tremendously high ceiling who can play in any scheme - that player is Miles Jack. The Bills used to use that approach and it scored them Sam Cowart and Thurman Thomas.
The Shaq Lawson pick, to my mind, was a shortsighted, bungled maneuver by a flailing regime on its dying gasps. Sorry if that sucks to hear.