Romans is speaking against the Judaiser heretics who claimed that as new Christians, one must also follow the law of Moses.
Paul asserts this is wrong. Practicing the Law was done in anticipation of the Messiah. Practicing after the Messiah had come was proclaiming a falsehood.
The Jewish Law doesn't save, and practicing it as Christians doesn't indemnify you from sin anymore than the Jews who practiced it before Jesus came. "All have sinned" and are in need of a savior, both Jews and gentiles and anyone who brinks the Law is necessary for salvation.
That's Paul's argument. He isn't granularly declaring who is sinful. Notice Paul is writing about actual sin, but original sin. Therefore, children have not sinned. Adults who lack the capacity to sin, haven't sinned. Those are exceptions. And of course, Jesus hasn't sinned. That's three exceptions for which Paul offered no provisos. He didn't, because none were necessary. He isn't writing about individual sinners.
Protestants who use this for that purpose are misappropriating the text.