My understanding is this.
We all have sin (original sin)
4 people were born without original sin. Adam, Eve, Mary, Jesus. Adam and Eve committed the first sin and became the first sinners. Part of why we refer to Mary as the “new Eve” is because she, of course, did not sin, and Christ rights Adam’s wrongs. Scripture captures this with the idea that through one man sin and death entered the world and by one man it was conquered.
It is indeed accurate to say we are all born sinners, and we are. Through the stain of original sin. Which baptism clears us of. Then, there are millions of people alive right now who are baptized, yet lack the ability to sin. A baptized infant who dies was born into sin (original) but once that was cleansed (baptism) if that child dies before the age of reason which is sadly common for many, they would die sinless having never committed a sin.
In a state of grace, (which we are all called to be in) we are free from sin. Sin is not our identity in a state of grace. But in a fallen world the stain of sin (temptation) remains, meaning we can fall into sin and out of a state of grace.
So here is the rub. Protestants love to point out how sinful we are. It is almost prideful to see who can be a bigger sinner. It is a false sense of humbleness.
As Catholics we can say this. "I was born into sin, then I was a sinner, (now here we will have different answers. But I will continue with the assumption that the Catholic stating this is in a state of grace and free from attachment to sin.) I was cleansed of sin, I am currently NOT a sinner, and even though I MAY become a sinner again, I also MAY NOT. And the goal (and it is attainable) is to remain sinless.
In short, you can add to your list of Mary and Jesus, for sinless people, children who were baptized and died, anyone in the state of grace and free from attachment to sin currently, Baptized people who lack the mental capacity to sin even in adulthood, Anyone who has ever died obtaining an indulgence and fulfilled the requirement to be free from attachment to sin.
So, billions of people. You could say they were sinners, but you cannot say they all sinned or that any one person WILL sin in the future thereby making them a sinner.