Here’s my take: the answer is emergent phenomena. We live in a very complex system and in complex systems there are interactions that can only be predicted using systems of equal or higher complexity. So even in case everything is predetermined, it would still be unpredictable and therefore your decisions are basically still up to you and the complex interactions in your brain.
This is the problem of original intentionality. There are studies on it, for instance they found that with an mri they can detect when you have come to a decision before your conscious mind realizes you have. Some processes in our brain are outside of our control, because the brain is not just the neocortex but also includes tens of other structures that evolved separately with specific hard-coded purposes, but that doesn’t mean they are not working as a team. I think in any case you are still reaponsible for the decisions you take.