I think this analysis ignores that the Republican party is winning because they expanded their coalition outside of their base of religious and upper-income voters. Trump pulled in lots of either non-voters or formerly Democrat voters. That's hurting the Dems it has made them more uniformly the party of the educated and upper-middle class and losing broader appeal The flip side is that the GOP now needs to manage a more diverse (racial, religious, cultural, income) coalition along with that. Trump is unifying to across the coalition to a large degree but its hardly assured that his successor will be able to continue that.