It has helped me to remember that Dunning-Kruger has 2 sides. Beginners tend to fall in the "don't know what they don't know" category, which can lead to over-confidence. But the other side is under-confidence on the part of mid-to-senior level folks. Those with experience start to see that there's a lot they don't know (i.e. they "know what they don't know"), and there's a natural overlap between this state and the state of impostor syndrome.

This doesn't always mean that you're an expert if you feel under-confident (I wish that were the case haha). But it might mean you're moving out of the true beginner quadrant and into journeyman status.