Firstly, and most obviously, we need to recognize that “all” doesn’t mean “everyone without exception”, but rather, “everyone, without distinction.” Paul is asking his audience if Jews have “any advantage” over the Greeks (gentiles). When he says “all”, he is referring to both the groups he was discussing. So, both groups have sinned.
Secondly, if we take “all” to mean “everyone without exception”, then that necessarily means that newborns, children, and even Jesus, have sinned. That puts us in an awkward position.