Endgame is a modernist play because it attends to the major characteristics of modernist theatre which include:
1. A detachment from romantic heroes, emotional plots, extended stories, and sticky topics.
2.Wittier language and the integration of modern problematics.
3.More realistic situations that reflect our psyche and human nature.
4.The exploration of common issues
5.No more idealizing society, modern theatre was the equivalent of "reality" theatre.
Beckett, born in Ireland, is one of the most recognized modernists.
I agree with the person above me lol