Great point. Edelman had 850 receiving yards last year. No 33-year-old receiver had that many in 2018. Fitzgerald had over 1,000 in 2016 and 2017, and five guys beat 850 in 2014 (Anquan Boldin, Malcolm Floyd, Steve Smith, Roddy White, Andre Johnson), but it's pretty rare. Randy Moss was as much of a freak as anybody, and he dive-bombed off a cliff at 33 (went from 83 for 1263 and 13 to 28 for 393 and 5 with three different teams).
I would say it's an interesting group of receivers with pretty wide error bars.