I think even if India had scored 300+ runs it would not have been too difficult for Australia to win the match. Because they went on the field without the preparation that Australia will win the 2023 World Cup, where the Australian captain said they have the experience of how to play the World Cup. Although 300 plus runs would have been difficult for Australia to win but India could not make it.
I totally disagree with your statement because if India scored 300 plus then it will be like impossible for any team to chased such high target under pressure of final and some magnificent bowling of you opponent trio, no doubt Australian has good history in ICC ODI World Cup and they always done decent in last stages of World Cup but they way indian bowling get rythm through out the tournament and performing majestic performance will make really difficult for Australian to cross such high target on thier home ground. Anyway the unfortunate dismissal of Virat Kohli really change entire things for india because when he lose his wickets entire Indian team lose his confidence and Thier body language indicate that they already lose match before it actually come to end.