There are several matters here that should not be confused. However before proceeding, we should note that Paul's teaching on human sexuality was, for the time quite radical - homosexuality (in its various manifestations) was extremely common and regarded as perfectly "normal" in Roman culture.
First - Paul is judging no one in 1 Cor 6:9. He is stating a fact (as he understands it) that sinners of various kinds, those who deliberately sin despite a knowledge that God disapproves, will not enter the kingdom of God.
Paul was well-aware that God does not judge the ignorant as he states in Acts 17:30. Therefore, God cannot and will not judge people for what they are unaware.
Thus, Paul is making no comment about any particular person - judgement is left to God alone. Paul is making a very general statement about who will enter the kingdom of God.
Those in secular Roman culture would not be among those who held such views about human sexuality and homosexuality because most regarded this as acceptable. Thus, Paul's comments could only apply to those familiar with Bible teaching.
Second: We must treat very carefully about what 'homosexuality" 9in its various manifestations means. Jesus is quite specific about this area. He says that, (Matt 19:11, 12)
“Not everyone can accept this word,” He replied, “but only those to
whom it has been given. For there are eunuchs who were born that way;
others were made that way by men; and still others live like eunuchs
for the sake of the kingdom of heaven. The one who can accept this
should accept it.”
The same idea can be applied to homosexual people - there are some that are born that way and other who have decided to be that way. If a person finds themselves born with homosexual tendencies, does that mean they are forever excluded from the Kingdom of God? Of course not! We ALL have our weaknesses and tendencies to sin which vary from person to person.
Now let me be very frank - some argue that because SOME homosexual people are born that way, that makes the practice of homosexuality for them acceptable. Unfortunately, there are also some who are born with pedophilic tendencies - does that mean that they and their practices should be acceptable. Or what of the person with a hyperdrive sex urges who wants to be very promiscuous? None of these practices should be acceptable just because a person is born with such defects - we all have them is different ways. See Rom 3:10-18.
God is gracious and kind and "helps us in our weaknesses", Rom 8:26.