Unless I misread it, it sounds as if you're saying that CD doesn't have the measurables to have much of a ceiling. I've got him listed as 6'2" and 198 pounds. He ran around a 4.5 40. He's incredibly hard to tackle. His best asset is his precision route running and terrific hands. In my opinion, his ceiling is in the Jerry Rice territory. Rice was 6'2" and 200 pounds. Rice ran a 4.58 at the combine in 1985. Rice is considered by many to be the GOAT because of his route running, amazing hands and RAC...the very same things CD is noted for.
By measureables alone, you wouldn't have seen it in Rice either. CD was a rookie last year. He only needs to improve and then keep doing it for the next decade and a half. He needs to make around 13 probowls in 16 years. He needs to total about 23,000 yards to catch Rice. Heck, rice went for 1200 yards in the year he turned 40!
I don't compare CD to Jerry Rice because I think he's already there. Obviously not. I compare him because that's who he reminds me of. If I am to project out a max ceiling, that where I put it until it doesn't look like it's still possible. Odds are always that a player won't be the next Rice. Always. Until some kid is.