The argument in the OP is subject to Kant's argument about how free will is possible, given the strong distinction between the "thing in itself" and the world of the phenomenal
, that is, the world of "appearances" - I will elaborate.
The argument of the OP appeals, at least implicitly, to the law of cause and effect. More specifically, I assume the writer of the OP would say that any decision I take is "caused" by chemical reactions in my brain, all of which are grounded in the laws of physics, and not in the "will" of any agent. In short, the laws of physics, perhaps combined with random chance, are fully causally sufficient
in respect to any action I might take. Fine.
But Kant argues that the law of cause and effect is something our minds "impose" on the data of sense experience that is given to us
(Kant also argues that our minds structure the raw data of sense experience in other ways as well). Futhermore, we simply cannot
have access to things as they are "in themselves". And one of those things is me. So, Kant would assert (if I understand him) that while our minds necessarily think in terms of cause and effect, and this invariably forces free will out of the picture as the implications are unpacked, the entire "cause-effect" argument only applies to the world as we "see and undertand it" (the realm of "appearance"), and not the world as it is "in itself".
This leaves open the possibility that each of us, as we are in ourselves, can indeed act freely. And, of course, we cannot imagine how that would work precisely because we are "trapped" in the mode of only having access to the world of our "experience", and in that domain, we cannot help
but think in terms of cause and effect.
I realize this argument is pretty loose and I can imagine some objections, but there it is. The key point, I think, is that it is at least plausible that the very thing that seems to rule out free will - the unavoidable chain of cause and effect reasoning that results in attributing all our choices to the entirely "will - less" forces of the fundamental laws of nature, may really only apply in the world of "appearances", and not in the "real" world - the world as it truly exists.