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.
Indian bowlers played well throughout but there is a problem with the batting of Australia, as we have seen them how amazingly their reached it and how brilliantly they were fulfilled their dream of winning the World Cup. First thing is that India was good in both bowling and batting till the end of the World Cup but in the Final they were looking completely different. Nor their openers provide them a good start then the middle orders wickets were just falling and falling.
These all things matters, this was the plus point for Australia that there opener batsmen Head made runs for them, on the other side Indian openers didn't made the runs which were expected from them. Another thing is the middle order of Australia performed well while the Indian batters who come at middle order didn't perform well that's why they lost the final.