Which experienced receivers -- Jordy and Janis? They'll miss Jordy's knowledge and chemistry w/ Rodgers, but he struggled to separate from CBs. As for Janis, the rookie class will have to play STs to make the team, they have enough size/speed to do that.
Graham should replace Jordy's production, a rookie will replace Janis.
Not sure how you figure Adams is unproven. He was the best receiver last year. I agree they lost experience, but that happens to all teams, and given Cobb, Allison, Davis and Yancey have all had at least a year they should be ok. It might happen, but assuming all the rookies will flop or get injured is a pessimistic take.