The Bills lost their #1 and #2 WR from last year (whether we like it or not, but that is fact). They also moved their #3 WR (Shakir) to a #1 WR role. Finally, they did not bring in a #1 or #2 (It could be argued that Samuel was a #2 at the minimum, but we have barely used him to be called a #1 or #2). Besides these, we have replaced a few journeymen WR in Sherfield and Harty with Hollins and MVJ and that. hasn't worked out. WR is all about having chemistry and right now there is none, including with the two TEs.
This pretty much sums up the Bills struggles.