That's the problem with determinism. The thought of being capable to make your own decisions. This is the very illusion underlining the problem.
Though it can not be proven (since we can't observe more than one outcome at a time) it seems possible that determinism is at play here.
You see yourself capable of making your own decisions. We all perceive ourselves as such. I can now go to the refrigerator and grab a bottle of water. In doing so, I feel like I made this decision.
But the determinism behind it assumes that it was already decided that I'd go and grab a bottle of water before I had that idea.
Making the decision might feel like my own freedom. But having the idea to make that decision was predetermined.
I could also decide not to go and get that bottle of water. Now it looks like I'm in charge of whether to go or not to go. But whichever I choose, is the predetermined outcome. Meaning that while I have the option to choose now, whichever decision I make is the one decision that was supposed to happen in the first place.
And that's precisely why I say that it does not matter. It's merely a philosophical concept. I will still go or not go to the refrigerator. I still will pick one of the two. It's just afterwards, that one can say "this was supposed to happen". If I go, it's because I was supposed to go. If I don't, it's equally because I was supposed not to go.
It's merely a thought experiment to say that "uncertainty does not objectively exist", it does for us, but not for the universe around us.
Just like "history is written by the winner", determinism is written by choices already made.
It's a bit like the particle-wave duality in quantum mechanics. Both are true until you make an observation. Then, only one of the two remains true. It's a paradox.
Determinism is like a guy from the future who talks to you and ends all your sentences for you because he knows exactly what you'll say.
Which for us really changes nothing. We still don't know what we'll say until that moment comes. So we still live in complete ignorance of our future. To us, it's still undetermined.