I’m not sure what your point is. SF has devoted a ton of high picks to their D-line in the past four years, but until they got Bosa with the second overall pick and Garoppolo got healthy, it wasn’t really working out for them. Plenty of other teams have gone bust by using a ton of draft capital on the D-line (Jets, Redskins). It’s not necessarily a sure path to success just because one team has done it.
McDermott is really good at finding DB talent and he hasn’t needed top 5 picks to do it. That’s every bit as valid a way to build a top defense.
If the Bills have a chance to draft the next Nick Bosa, should they? Of course, but that’s going to be pretty unlikely, picking in the 20s. It’s always nice to have a great edge rusher, but anyone watching the Bills this year knows that probably shouldn’t be their top priority come April.