The current legal standard for 1A protection is “imminent lawless action” from Brandenburg v Ohio. Shouting fire is from an old standard “clear and present danger”. You can look at their respective wiki pages for details and definitions.

The history of Free Speech in the US is pretty interesting. The kinds of things that are acceptable today would get you thrown in prison 100 years ago (for example, handing out anti war pamphlets) and are more akin to the kinds of things Americans look down on other countries for criminalizing.

Nothing is set on stone and to accommodate changing times and values there should be a reasonable pathway to change.