Phizzy,. It has been debunked from the angle of it starting at Jerusalem's destruction in 607. Which originated from Nelson Barbour moving the date of Jerusalem's destruction 20 years because that would just leave a 50 years captivity.
But the gentile times understanding preceded Barbour and Russell in that it was not based on Jerusalem's destruction but on the invasion in the time of 605-607. So they have been debunking from the wrong point of view.
Russell had a wrong belief, they attack Russell's belief only, but that does not declare the times of the Gentiles itself to be wrong.