That's always been a feature of the 2-party system. I mean, the Democrats were once the party of southern white supremacists. We don't really get new parties, but the parties we have change over time as the coalitions within them rearrange.
I think a multi-party parliamentary system would be better at finding middle ground, but it's silly to say that the two-party system keeps politics "fixed".
True, the make-up and priorities of both Republicans and Democrats have changed a few times over the years.
I would say that in this case, it's a party aligning to an individual far more than it has ever been in the past. Racist Southern Democrats didn't become Republicans because they were enamored with a Republican leader, they changed parties because they found themselves misaligned with the Democratic Party's pivot to civil rights.
I wholeheartedly agree that a parliamentary system would serve the US better.
I think a multi-party parliamentary system would be better at finding middle ground, but it's silly to say that the two-party system keeps politics "fixed".