True conservatism has never been tried :)
The problem with your analysis is that you don't have the power to define what conservatism is; if enough populist reactionaries wrap themselves in the mantle of conservatism (which they absolutely have) then they gain effective ownership of teh term and ruin it for everyone else. I agree with your general thesis but think the rot goes back longer than 3 decades, although it got markedly worse after Newt Gingrich became speaker, around the same time that Fox News started on cable.
As an example, consider Phyllis Schlafy's 'Eagle Forum'. Founded in 1972, its always been a reflection of its late founder's strident reactory outlook, to the point that their periodic rants about communism seem quaint and anachronistic. You could be forgiven for thinking it was relevant for political scientists studying the American right in the 20th century...except the US attorney for DC (a guy named Ed Martin Jr) is an Eagle Forum veteran, and a glance at his X timeline shows he's still all in on la Schlafly, doing official government business through his X account (eg publishing documents ther and nowhere else), and generally living down to the stereotype of a wild-eyed ideologue.
In short, I don't believe terminological exactitude isn't going to get us out of this. The famously cranky Samuel Johnson, writing disdainfully of a British Prime Minister in 1775, commented 'Patriotism is the last refuge of a scoundrel'. His point was that any concept invested with general-purpose social value - patriotism, love of nation, belief in community, conserving the body politic - can be exploited for short-term political gain to the detriment of long-term well-being. It's a perennial problem.