You aren't the only fantasy owner to ignore - all summer long and into the season:
1. Change of coaches (fired were the guys from last year).
2. Change of offense (former Saints coaches literally said all summer that MW gets the position that Mike Thomas played)
3. Herbert has different strengths than over-30 Rivers did. Rivers dumped off a lot of short balls (slot, RBs, and TE) and then took bomb shots. Herbert just may be the opposite by going deep (MW) more often and less short stuff (KA).
4. Allen plays the "other WR" spot that highlighted E Sanders, Ginn, TreQuan, Snead, and Cooks, but Allen isn't a burner threat like most of them.
5. Mike Williams is a talented first round WR that was misused compared to his strengths and can't stay healthy because he sacrifices his body too often on highlight reel receptions. If he stays healthy, they re-sign / franchise him.
6. If MW gets hurt, Allen probably doesn't switch positions on the field
Just my opinion.
I know you said in league chat "we know what Mike Williams is by now", but sometimes the coaches aren't blowing smoke. It's not the Brees/Rivers short game offenses. My analogy is what happened to "Thielen" (minus the TDs) when Jefferson was utilized to his strengths. Still good, but not going back to years past.
I'll probably be wrong and MW gets hurt in his next game and Allen has a second half season revival.