BaZi's answer is nuanced: your chart is fixed, but your response to it is free.
Your chart is like a hand of cards dealt at birth. You can't change the cards. But how you play them, when you bet, when you fold, and who you play with — that's free will.
Your Luck Cycles are seasonal weather. You can't turn winter into summer, but you can build shelter, store food, and plan for spring. Some people are dealt difficult charts and play them brilliantly. Others are dealt favorable charts and waste them.
BaZi doesn't predict a fixed future. It reveals your tendencies and timing — and within that framework, you choose. Every choice either reinforces or redirects the energetic current you were born into.