The democrats’ economic stances are a good example of this: they've moved towards neoliberal economic policy since the 80s, to the point where the democrats and republicans have a materially indistinguishable stance on unions, workers rights, public benefits, Wall Street, etc.
This may seem like nit-picking but I think it’s important to clarify that some policies that lie outside the overton window are “extreme” because those in power want them to seem extreme, not because they are actually unpopular or unrealistic.
This may be wrong, but when I think of centrists I think of people who decide where they stand on each policy on a spectrum that extends from what the Dems deem acceptable to what the Republicans deem acceptable. If you’re someone who decides where they stand on an issue regardless of these arbitrary endpoints I think “independent” or “non-partisan” fits better.