A consequence of the fact that Heaven is hierarchical is that while almost everybody is indeed a sinner - some people are better (i.e. Holier, more advanced spiritually) than others.
The advantage of acknowledging the reality of Saints is that these were people who were without sin ( in the sense of already being continuously in communion with God) - and progress towards, or away from, this state is quantitative.
The only thing is that we should not make this judgment about ourselves, because of the danger of pride.
However we can, and should, make a judgment about the relative Holiness of others. How else could we be guided?
These judgments will not (in this corrupt world) be wholly reliable, and we may need to change our minds, and we should make judgments in light of the wisdom of the Church through the ages and by asking for help in prayer and not by our own individual unaided analysis; but we must perceive that Holiness is hierarchical and make judgements about its presence and degree.
Holiness is not egalitarian.