Is there a difference between modern tafseer of the Qur’aan and ancient tafseer?

If what is meant in the question is the tafseer of the Qur’aan during the Umawi (Umayyad) period at the time of the righteous salaf (predecessors) of the Taabi’een and the successive generation, and the lesser Sahaabah, the compilation (of tafseer) in written form was not widespread at that time, compared to later times. It is mostly limited to reports which are known as al-tafseer al-athari (reports quoting the words of the Prophet (peace and blessings of Allaah be upon him) and the Sahaabah).Then the scholars adopted other appraoches in tafseer and followed a number of trends, some of which were praiseworthy and acceptable, and others were to be rejected. In more recent times, this reliance on their own opinions and understanding was taken even further, and theories and variables which have no place in tafseer were forcibly introduced. It reached the point where it may be said of some tafseers that they contain everything except tafseer. Examples of this in mediaeval tafseers include Tafseer al-Raazi, and in modern tafseers, Tafseer al-Jawaahir.

One of the good references on this is Ittijaahaat al-Tafseer fi’l-Qarn al-Raabi’ ‘ashar by Shaykh Fahd al-Roomi