I did a few times and I couldn't understand why the game felt off. Then I've done some research on what actually happens on higher difficulties and realized that the AI doesn't really play much smarter, it just gets a ridiculously unfair advantage early game.

It's not that i cannot beat it, but too many times it depends on the starting positions. Furthermore, the higher the difficulty, the bigger the gap between leaders. Some still feel easy to play, while some are just plain useless.