endgame is the best game
One of my coaches in High School used to tell me that not all games have endgames but all games have endings. That being said, if you study endgame theory, when you do get to ones you will have a lot better odds of winning in drawn positions, drawing lost ones or just outright smoking your opponents off the board.
So this is an example of an ending I played like 20 years ago that sticks with me. It utilizes understanding imbalances, passed pawns and sacrificing for a win. There are some subtle parts to look at but it's a pretty good idea of how studying endgames can be of benefit.
Here is a recent example of how better endgame play saved a win in a losing position.
The game turned around at about the 40th move. Follow along in the ending from near move 43.