[naasking]

> If free will exists, that would seem to imply that people can make decisions that affect their future.

Yes, and this is trivially true. I will demonstrate: you must now make a decision whether or not to lift your arm overhead. Whether you lift your arm or not, you manifested that future by a choice.

People who make claims like yours typically misunderstand either what's meant by "you" or what's meant by "decision", typically the latter.