I don't think Remi can change the society. While he has leadership skills and has a 'good' vision for his tribe, his personal qualities disadvantage him from making the necessary changes needed in his society. These qualities also make him an ineffective leader.
First of all, he is haughty/proud. He feels he is superior to others. He is better off than others. How can you help others or bring the changes in society when you think lowly of the people?
Jane tells Remi before the breakup, "You don't know yourself, or what you really want. Only that you like thinking yourself a delicate being, superior and so much better than anybody else "
When you want to deal with issues that affect the people in society, you have to approach or deal with issues in a professional manner. You can't demean the people who practice what you think isn't right or think you are better positioned to deal with the issues than others. Also, you can't disrespect people because of what they do that contributes to the problems in society. Remi showed a lack of disrespect to his mother because she had forced him to marry Think. Also, he spoke ill of Think. Instead of addressing his concern to the concerned people (in private), he talked openly (in front of people). This is a negative trait that shouldn't be part of a leader.
His pride and how he behaves towards other people is revealed in the manner he responds to his mother. "Everything will give way to my leadership."
He thinks he knows better because city life has taught him everything. However, at the death of his wife, we learn he does know much.
When the pastor insisted Remi should return to his homeland, he turned towards him with an ironic smile. This ironic smile was the cause of the death of his wife. He thought he knew better and would deal with the issues in his society his own way.
To make changes in the society, you should listen to others. Your own views won't help. Also, as noted above you shouldn't address people in a manner that shows you know better than others.
The woman who handed Remi the letter that was written by Thoni tells Remi, "You are a leader! Our leader indeed. Know you not what you have done? Flint insults at your own tribe, trampled mercilessly on wives everywhere? You may praise yourself (how you have succeeded in politics). What of here? What have you done to the lives of many? To the hearts of many a man who looked up to you for guidance?"
However, it might be Remi can make the changes needed in society. Why? The death of his wife (suicide) taught him something. He says while mourning the death of his wife that he came to deal with tribalism and customs of his tribe but his actions led to his wife committing suicide. It might be he learned his errors or gained a new perspective on what leadership entails and what is required (he needs to do) to ensure he brings out the changes needed in the society. It might be he reflected on his personal qualities and the need to change them. We might never know whether he changed after the death of his wife. There might be some hope that he changed for the better.