Brandenburg overturned the specifics of Schenk, not the idea of free speech having limits. "There are valid limits of free speech" remains as true as ever.
I'd had a paragraph after that said "You can, in fact, yell "fire" in a crowded theater without breaking any laws", but edited it out because in certain situations this would also violate the revised test in Brandenburg (you still can't incite a riot legally, for example). But that paragraph made it a bit more clear that yes, the irony I'm talking about is that the specific examples in Schenk are no longer law, not the general principle that free speech has limits. The limits are significantly less restrictive than Schenk held, though.