Yes, it's my understanding that, in practice, Kessler syndrome would most probably mean no geosynchronous satellites. It's slightly reassuring that that isn't as horrifying a proposition as it was thirty years ago. Recent advances would allow things like geonavigation and telecommunications to be supported with Starlink-style low orbit networks, even in that event.

Regarding simply transiting through our ex-satellite rings, I don't think there is consensus. Would it make launches beyond LEO practically impossible, or just theoretically risky in the way that blindly navigating the asteroid belt is? (You could hit something, but it's so little matter dispersed over so much space it'll probably just be extremely fine dust the shielding can handle. Probably.)