Every decision is a product of your experience and state of mind, that are the product of you previous decisions, that are the product of your previous experience.. something, something!
You can go get another beer, as would be expected given you had three previously and chose to come to a bar, or you can choose to go home and sleep, or get in your car and drive, or swear off drinking forever.
The fact that options are present to you because of your previous choices (causality) is irrelevant to the fact that you still have full control over what option you select (free will).
We'll never know anyway, but I feel like there would be nothing, no universe, no life, no space etc... if there was not this "random" thing.
Nevertheless, I agree with your critique of determinism. Think outside the "system". Nobody knows why stuff exists or why it behaves the way it does, it's all just observation and ideas.