Given the Pats' history of difficulties integrating new pass-catchers (WRs & TEs, primarily) into their offensive system ...
And given the fact that three of the Pats top pass-catchers from last season became suddenly and unexpectedly unavailable at the last minute (plus, Bennett was gone in FA) ...
While I, too, have not been "Wowed" by any single play from Cooks (comparisons to Gronk are kinda unfair here), I think Cooks' body of work for the season has been pretty impressive.
Looking forward ...
There's tomorrow and (hopefully) three playoff games remaining (including the SB). There's at least some possibility that both Mitchell and Hogan are back on the field for at least some of those, legitimately drawing coverage away from Cooks a bit. So, there may be some opportunities left for Cooks to make a "Wow" play or two yet this season.
Then there's Free Agency, during which we'll see what actually happens to the market price of veteran WRs in 2018. At this point, we only have the Jeffery and Adams contract extensions to go by.
After that, there's the draft - which may or may not bring another 6-8 really good, young WRs into the market.
After that, there's the Pats own roster-building process through OTAs and into Camp, during which time BB and the coaches will have further opportunities to observe what more Cooks may be able to do (and Amednola/Edelman/Hogan/Mitchell/Dorsett/whoever).
So, the Pats don't really need to decide on an extension offer amount for Cooks until they have more information, and there's a lot more of that coming.