Actually, in the past 3 years, only Watkins has caught 60% or more of his targets and averaged over 17 YPR (and caught 40+ passes). In 2015, Robinson was at 53% and last year DeSean Jackson was at 56% to give a couple examples. So Stills' numbers are not out of line. Sorting by 13ypr<x<14ypr and at least 50 rec, Parker (64%) is pretty close to the median (62%) over the past 3 years. I doubt Parker ever commands 169 targets in a season nor approaches 1650 yards. I honestly think he's only about 50/50 to ever reach 1000 yards in just one season.
FBG data is a little sketchy... they list 10 targets inside the 20 in his splits, but their red zone target summary only lists 9. Either way, he does get more targets there than Stills (6 is listed in his splits and 7 in the RZ summary). Jordan Cameron is vacating 14 RZ targets. Landry got a whopping 23 last year, resulting in a stunning 3 TDs.