The Thanos we see in Avengers: Endgame is a very different person from the villain we meet in Avengers: Infinity War, due to Endgame Thanos being four years younger.
The cut scene would have gone a long way towards establishing the ruthless nature of Thanos.
Avengers: Endgame shouldered the responsibility of bringing together and sending off MCU characters developed over a decade.
Many viewers felt that the Thanos we got to see in Endgame was a much more uni-dimensional version of the character we got to know during Infinity War.