I've got a 24-70m and like it. It wobbles slightly, but not so much that ever post a thread about it. Rather the annoying zoomcreep which renders it useless on certain long exposures from a tripod.
I've brought some of my lenses to Canon for adjustment of mechanical parts. You might want to do that. I know your problem so well: I'm I obsessing or are my totally expensive lenses crap? And who can you ask - nobody.
My cheapie 28-105 F/4-5.6 Canon zoom wobbles a lot. The outer part can move a couple of millimeters side to side with a gentle finger push, but it seems to spring back ok. I would certainly have to be careful not to bump it during a long exposure, but otherwise it takes surprisingly sharp pictures (for its price point). My L lenses do not
wobble, and I would be quite annoyed if they did. I'd ask Canon to check it out.