"Medieval" is certainly still used.[0] "Dark Age" is no longer used interchangeably with Medieval, however. This is because many now see the period starting from the High Middle Ages in Europe as directly leading to the modern period. Refering to the entire Medieval period as a Dark Age is to take a side in that argument.

[0]https://scholar.google.com/scholar?hl=en&q=Medieval&scisbd=1