Kyoraku casualed Starrk (who's mere presence could kill Adjuchas - which by the way is a feat that none of the Quincy come close to besides Yhwach) - and it was prerequisite that to even withstand his presence (let alone completely neg diff in combat) you needed monstrous Reaitsu of your own, and you're here pretending Kyoraku isn't a Reiatsu monster as well... jfc people love to retcon things for the agenda don't they?
The way Kyoraku's Bankai works is it plays out scenes of a play. The are un-negatable. If a play has a murder in it, then Kyoraku's opponent will die unless his opponent can kill Kyoraku first. The only characters in the entire verse I'd be confident in saying could do that are Yhwach, Ichibe, Ichigo, Yama and Hogyoku Aizen. His Bankai would though, work on every character that wasn't a Schutzstaffel or Yhwach.
Kenpachi's reiatsu doesn't even compare to the top tiers though - let's stop pretending it does. He was clearly portrayed to be nothing out of the ordinary amongst even the captains during the fight with Gerard, which by the way was an 11 v 1 with captain class fighters across the board, while Kyoraku on his own was fighting Lille who was approx the same power as Gerard. If we're putting Reiatsu into tiers Kenpachi's sits on the same tier as Zero Division (besides Ichibe), whereas Kyoraku's by feats is in that tier at it's absolute lowest estimate but probably sits inbetween ZD and the top tiers.