If Fields plays the rest of the year like he has the last two games then yes, it would be very easy to pass on Williams. I am definitely higher on Fields than I am Williams.
A WR feels like a luxury item for a team that has more pressing needs. If you cannot protect Fields, then whats the point of having Marvin Harrison, Jr? I'd be happy to have MHJ, but the Bears do have more pressing needs. Build you damn lines before you start to acquire skill players.
As for trading down idea from another poster...that was needed last year but I believe the Bears need quality over quantity this year. That's why the Bears should keep both 1sts.