The first 3 things I look at when I am scouting WRs is this:
Route Running - because if you cannot run crisp routes, you will not create separation in the NFL and you will not get open.
Hands - If you cannot catch the ball or if you are constantly fighting the ball, I just cannot count on you in big spots. It limits your upside.
speed - Unless you are a detailed route runner, or have great size/length, you need to have some speed or at least be explosive.
Everything else is secondary IMO. Athleticism is nice, blocking ability is a bonus. knowing an entire route tree can be taught, strength can be added, run after the catch is nice, but a bonus. Etc.
Van Jefferson is a good, not great athlete, with average speed. But what he does, he does extremely well. He has great hands. Soft and natural, and strong. Never fights the ball, I want him as my partner in an egg toss competition and a picnic. The other thing he does really well is run routes, his dad was an NFL WR and is now a WR coach, so he has been taught how to properly sink his hips in an out of breaks, how to set up his footwork to maintain speed in and out and never rounds any route off.
So he checks 2 of the 3 big boxes off. I'm not worried about lack of production because Florida QBs have been horrible. But I think he is a 2nd round guy with what I would consider a high floor, low ceiling. Due to his lack of open field ability with a lack of HR speed, he'll never be a WR1, but he will make a heck of a WR2 or WR3 inside from the slot or from the outside. I think he is a less strong Juju Smith-Schuster. LARAM did not like JJSS as much as I did coming out because he just wasn't fast or super athletic. I loved him because he had good hands and got open. I think Jefferson is in that same boat, minus JJSS's strength.
Don't waste your time looking back, you're not going that way. - Ragnar Lothbrok