I'm not sure whether this is "evolution" or not. I think to the bands I like and listen to, and the VAST majority are not doing thing today that are radically different than from whatever their heyday. Paul McCartney is one of the most revolutionary bass players in rock, but is he REALLY furthering the instrument at this point? He's clearly not playing Jaco lines, but I'm not really ready to call him "complacent".
I have a LOT of criticisms about Kirk; I sometimes wonder what the f--- he's even doing at times. I've heard it posited that he's given up, he's focused more on horror films and his haunted house stuff, he's focused more on weed... whatever. But I wonder if he's just found that balance of his "style" and what the band requires at this time. Not my thing, but that doesn't mean it's bad, only that it's not my thing (honestly, I have a running debate with a guy I work with who reveres Kirk and I have no bones in telling him I'm just not seeing it).