I absolutely disagree, it's all about foresight and finding the right trade partner.
if this team fielded offers for Gilly lock 2 years ago, he would've absolutely fetched a first from a playoff team with DB needs. With a pending contract on the table, not so much, a la Jamie Collins. Sam Bradford is another notable guy who was traded at the right time to the right team and fetched a 1st, even with a decent sized contract.
Those other leagues throw around picks, but the NBA's "1st round" is not comparable to the NFL's. The top 10 or some years even 5 picks in the NBA are basically like 1sts in the NFL, because of the talent difference in prospects.
A huge "sell-off" may not be completely lucrative, but you'd still get a return that would be used for the future. Even if Kyle WIlliams only results in a 4th or 5th rounder, that's better than him retiring in a season or 2 with us after another year of mediocrity.
The Bills are going to make whatever decision they do about the organizations' future, but if they plan on going for a QB in 2018 or one in 2017 with a short term rebuild, you have to sell off some older guys or lose them for nothing. It's just that simple.