Political blogger Nate Silver and his team at FiveThirtyEight have repeatedly used DW-NOMINATE scores to gauge the ideological location of major political figures and institutions.[30][31][32][33][34]
It seems that 538 uses this method repeatedly, so it's accuracy does seem to be more than advertised. Then there's the evidence of Trump, DeSantis, Johnson, Green, Gosar, Gaetz, Paxton, etc to which there is no real response. I also see no arguments that the Left hasn't moved any, the opposite in fact.
The more extreme the parties get, the harder it is to meet in the middle. The fact that one of the parties has a large history of backstabbing, hypocrisy, & going back on agreements also hinders things, since if you can't trust conservatives in negotiations what motivation is there to try? Moderate & Conservative mindsets are absolutely necessary in politics, but with the madness infecting conservative philosophy these days it's hard to see a way forward when they won't do anything to police the behavior of their own. They have to be able to control the radical elements and accept the consequences for GoP officials/politicians when they are guilty of fraud, insurrection, or any other crimes they stand accused of. If the consequence is a swift trial that exonerates them then that seems worth it to me.
If political parties can't agree on things like norms, acceptable practices, and other basics of living in a society with others that ordinary people have to deal with, there can be no end in sight for this radicalization and the violence that comes along with it. If they won't do it by choice their voters have to find a way to show them it's unacceptable, and the most extreme case of that which doesn't get into violence is by refusing to vote for them en-masse and contacting them to let them know.