Except she very clearly is trying to contribute. Do you think it was solely Minfilia's idea to leave Ardbert behind rather than use his energy to stay the flood? Minfilia is a very smart and capable person, but I doubt she has the ability to recognize that someone's soul is the same as another's or the ability to pre-plan to such an extent that she can make a split second choice that affects 100 years down the line. I'm positive that either before or after she was sent on her way, Hydaelyn sent her a memo not to use Ardbert's soul.
There's only so much you can do when you quite literally have no way to speak to people, let alone actively influence events.