Coleman is definitely a fine prospect but he struggled to create separation regardless of who his QB was.
34.5% of his targets where considered "contested". This is defined as "a defensive back within close proximity to defend the pass". 34.5% is by far the highest % out of any of the top receivers in this class.
To put it into perspective here's some of the other top WRs in the class.
MHJ: 16.7%
Troy Franklin: 13.5%
Rome Odunze: 20%
Brian Thomas Jr: 14.9%
Now add in his contested catch % which is only 33.3% and you've got a big body receiver who struggles to create separation and then is sub par when it comes to catching said contested passes.