Agreed, Chase and Watson are even not close to comparable. Chase was coming off a year off after on of the top 10 seasons by a WR in college history and had no issues with drops.
Knocking the rust off after 18 months without live action is a bit different than continuing to have the same problem that you have had your entire life.
And I tend to disagree about the degree to which this can be "fixed."
Like any skill, you can maximize the level at which you can perform that skill, but there is also a proficiency range of that physical talent that you are born with. Watson is a height/speed elite talent with ordinary joe hand eye coordination. The first has trumped the second, at least to the extent that he could overcome division 2 level talent, but now he will be playing against guys that are within the same sub-class ht/speed, so I think the bad hands are likely to become a more noticeable issue at the NFL level.