switching from tolerating overt racism to tokenist and shallow identity politics isn’t a “significant change” in the Democratic Party

You're confusing a half-measure for nothing at all. Yes, taking big steps towards legal equality and dismantling the most obviously racist practices was a significant change from open segregation. Denying that real progress has been made -- however far we still have to go -- is out of touch.

Nor was embracing the religious right a significant change for the Republican Party

It was enormous change, and there were other enormous changes in the party, too. Compare the Eisenhower-era Republican Party, which had a strong isolationist wing and which was on board with significant infrastructure projects, to today's Republican Party, which is willing to crusade at the drop of a hat and which is far more opposed to the government doing almost anything else.