The New York Giants have underperformed for some time now. Seven double-digit loss seasons over the last eight years should pretty mush tell that story.
But there are plenty of other metrics that will expound the narrative further, such as Football Outsiders’ DVOA chart.
DVOA is described by FO as “defense-adjusted value over average breaks down every single NFL play and compares a team’s performance to a league baseline based on situation in order to determine value over average (regular season only).”