Maybe so, but it has a lot of truth in it. The areas of the nation that were Republican are now Democrat. The areas of the nation that were Democrat are now Republican.
The populations did not change their world views. The North East is still big city Hamiltonian liberals, and the Rural South is still Jeffersonian conservative. The labor union sections of the country are still the same as they were in the 1860s.
The labels changed, but the ideology has remained fairly consistent for the demographical area of the country in which it held sway.
NYC was always a big Democratic stronghold. And the cities where the supposed inversion occurred did have a huge shift in population demographics.
The GOP did not shift left in a big way until TR and “progressive” politics. The Democrats were left-wing long before that; it’s in their published views even from the nineteenth century, reflected particularly where then Princeton University student Woodrow Wilson said that “socialism and democracy” were “one and the same” and compared it even to Bismarckian state socialism (which spawned national socialism and the European Union’s social market economy).
Don’t forget that the fifteenth goal of the communists was to “(c)apture one or both of the political parties in the United States”.