Mick Lombardi is WR coach. I'm quite certain he has/is doing everything possible to help Harry become a better football player.
I'm also quite certain Josh, Troy Brown, JE11, Cam and others have provided him with help and support learning the offense.
You say things like route running, processing, physicality over the middle, are receiving qualities that can be improved on. I would agree but only if the player a) has that physical ability and b) has that desire. Due to physical and mental limitations some players can't run good routes, or are physical or process information/make quick decisions.
Maybe in 2021 it'll "click" for Harry. Maybe it won't. Who knows.