They wasted our precious times
The Avengers could have the ended Thanos' goal which was to let half the magnitude of life disappear in order to maintain balance when Spiderman almost had the gauntlet off his hand.
Then boom!!! there comes Quill...made his emotions get in the way
Raged Thanos then incited once him again.
That stupid anger cost us a whole avenger movie
Or was it a way to introduce some of their new character(s)?