I am certain that you understand that one someone is recognized as "blessed" and "Highly favored" by God, that they should be held in esteem
James 2:1-11 My brothers, show no partiality as you hold the faith in our Lord Jesus Christ, the Lord of glory. 2 For if a man wearing a gold ring and fine clothing comes into your assembly, and a poor man in shabby clothing also comes in, 3 and if you pay attention to the one who wears the fine clothing and say, “You sit here in a good place,” while you say to the poor man, “You stand over there,” or, “Sit down at my feet,” 4 have you not then made distinctions among yourselves and become judges with evil thoughts? 5 Listen, my beloved brothers, has not God chosen those who are poor in the world to be rich in faith and heirs of the kingdom, which he has promised to those who love him? 6 But you have dishonored the poor man. Are not the rich the ones who oppress you, and the ones who drag you into court? 7 Are they not the ones who blaspheme the honorable name by which you were called?
8 If you really fulfill the royal law according to the Scripture, “You shall love your neighbor as yourself,” you are doing well. 9 But if you show partiality, you are committing sin and are convicted by the law as transgressors. 10 For whoever keeps the whole law but fails in one point has become accountable for all of it. 11 For he who said, “Do not commit adultery,” also said, “Do not murder.” If you do not commit adultery but do murder, you have become a transgressor of the law.
No matter how it's rationalized, esteeming another person as Catholics do to Mary and then the saints, is yet another direct violation of a clear command of Scripture, that is to not show partiality to people.
Now let the fear of the LORD be upon you. Judge carefully, for with the LORD our God there is no injustice or partiality or bribery." (II Chronicles 19:7)
But of these who seemed to be somewhat, (whatsoever they were, it maketh no matter to me: God accepteth no man's person:) for they who seemed to be somewhat in conference added nothing to me: (Galatians 2:6)
Then Peter opened his mouth, and said, Of a truth I perceive that God is no respecter of persons: (Acts 10:34)
Who shows no partiality to princes and does not favor the rich over the poor, for they are all the work of his hands? (Job 34:19)
For God does not show favoritism. (Romans 2:11)
And masters, treat your slaves in the same way. Do not threaten them, since you know that he who is both their Master and yours is in heaven, and there is no favoritism with him. (Ephesians 6:9)
For the LORD your God is God of gods and Lord of lords, the great God, mighty and awesome, who shows no partiality and accepts no bribes. (Deuteronomy 10:17)
There are more, but I think the Lord has made it pretty clear that we are equal in His eyes and one person does not hold sway over Him more than any other person. Honoring someone who is a example to us of faith and strength is good, but we must realize that people are prone to adoring and worshiping idols - of all kinds - and that does not honor God.
It isn’t showing “partiality” to call Mary “Blessed”. It’s quite Biblical.
“Blessed art thou among women...”
If, in the Bible, an angel calls Mary “blessed’, we can’t err in doing so as well.
It seems quite convoluted to claim that in doing so, one commits the sin of partiality.