Here are White's approximate values from PFR for 1986-92 with PHI then 1993-98 with GB...
PHI: 19, 15, 19, 18, 17, 19, 15
GB: 15, 15, 15, 18, 15, 16
He was diminished from his peak as a younger man, sure, but hardly a shell. He's the oldest DPOY winner ever at age 37 in 1998 and was 1st or 2nd team All Pro each of his six years with the Packers so he was playing at a top level right up until the end.
Would love it if Parsons topped Reggie's 68.5 sacks and 94 AV over six years with the Packers, but that is a pretty tall ask. Anchor a defense that wins one SB and he'd put himself right there with Woodson (DPOY, 4 of 7 years 1st or 2nd team AP, 74 AV) for me, but I give Reggie extra credit for the intangibles & culture change he helped kick off so Parsons would pretty much need to anchor two SB winning defenses for me to put him over Reggie in terms of impact.