the GOP has gotten more extreme in many ways

They ate the Dixiecrats, who were already openly white nationalist. But it's the same extremism, just migrated from one party to the other by way of the oil and automotive industry barons.

Looking back at what the John Birch folks said back then, it’s a lot more mainstream.

The Birchers were mainstream. They got Goldwater in '68 and Reagan in '80. The Tea Party and the MAGA movement can trace straight lines back to Bircher organizers and funders.

I’m just not as confident that the anti democratic sentiment isn’t just rhetoric meant for political theatre.

The problem is that most of the damage is already done. The VRA has been shredded. House seats are heavily gerrymandered. Systematic disenfranchisement is institutionalized. Media is captured by corporate interests loyal (or at least amenable) to the party. There's not a whole lot left to dismantle. Republicans have heavily entrenched, functionally unassailable state level majorities across the country.

The real threats the GOP face are from within - business and paleocon wings feuding over orthodoxy like 12th century Popes.

And democracy at least keeps this kind of fighting civil. Which is its purpose. Give people a non-violent outlet for civic participation, but limit the terms of debate to what the elites desire.

Nobody currently winning wants that system to change.