In principle, the OP is perfectly correct; but in the context, not.
If all have not sinned, & all are not under judgement for sin in consequence, not only is the argument of St.Paul made ridiculous & incoherent (in view of what he has already about the shared sinfulness of Jew & Gentile); but, in addition, all cannot receive grace.
Only sinners need grace - the righteous don’t; & this is one of the great paradoxes of the Gospel, that God justifies the ungodly, the guilty, those who deserve death. The righteous need no expiation for their sins; the Father “put forward” His Son as the propitiation for our sins (see 3.25). All that becomes meaningless, if all do not stand under the righteous judgement of God for their sins.
The doctrine of the CC cannot be built upon a basis which nullifies the teaching of the Apostles - it must find another basis instead, one that leaves St. Paul’s words & argument intact.