Larry Fitzgerald 4.63
Jerry Rice 4.71
Cris Carter 4.63
Anquan Bolden 4.71
Chad Johnson 4.57
It's also worth mentioning there are countless 4.2, 4.3 guys that hardly ever see the field. Being a WR in the NFL has more to do with route running, blocking, and good hands than it does speed.
What you said is mostly true. Speed is not a requirement, but if you're slow (i.e. in the mid 4.5s or worse) you better be big/physical (Michael Thomas, Larry, Anquan) or have a GOAT throwing to you. Because you can be on your route, but if you have a terrible QB, a HoF career can quickly devolve into nothing.
However, to be fair, we can look at the current leader board, most of which are going to be 4.4 guys, some 4.5s, some 4.3s or the All-Time and it will show a similar story.
#1 Jerry Rice - definitely faster than 4.71. Parcells says he consistently ran mid-4.5s. Rice wasn't elite speed, but he was fast.
#2 Larry Fitz - monster.
#3 Terrell Owens - 4.41
#4 Randy Moss - 4.25
#5 Isaac Bruce - 4.48
#6 Tim Brown - 4.46
#7 Steve Smith - 4.37
#8 Marvin Harrison - 4.38
#9 Reggie Wayne - 4.45
#10 Andre Johnson - 4.39
So Gil Brandt, in his famous evaluation and reasoning behind formulating the 40, was right. "4.6 and slower has a 1% chance of making a Pro Bowl, and 4.4 is the benchmark for elite speed". I'd say those figures are shifting because that was in a time when most Safeties were 4.6 guys and LBs were oftentimes 4.7/4.8 guys. With a lot of LBs being sub 4.7 guys, your WRs have to have speed to stretch the field.
The 40 is not the one-all-end-all but it does showcase critical metrics like short-burst acceleration and how long it takes you to get to top speed and what that top speed is.