> Japan was a pretty xenophobic, unified, and militarized place when the Europeans showed up.

Other than unified, that describes most places in the 15th or 16th century.

> Because, if you use sufficiently Eurocentric metrics, it usually was.

The one country in Asia* to not suffer colonialism (Japan) is way ahead of all the others that did have it, especially on "Eurocentric" metrics such as GDP and productivity and democracy and human rights. That alone should be a rebuke to colonialism's purported development powers.

* Arguably Thailand is another but it was forced to cede land to colonial powers. It too is considerably richer than its immediate neighbors.