Has Dragon Ball Super Broly changed the original Dragon Ball story?
The scenes in original anime were filler added by Toei Animation. So the new story does not contradict the original manga written by Akira Toriyama. Also Toriyama had released a manga called Dragon Ball Minus which is the story upto Goku being sent to Earth. In this manga, Goku is shown wearing a saiyan armor and is 3 years old. As the Dragon Ball Super Broly movie is written by Toriyama, the same details are included in the movie as the manga.

As the anime was dependent on the manga, Toei Animation had to add many fillers to make sure the manga was ahead of the anime. Hence the discrepancy.