The Church doesn’t make saints like a baker makes bread. The Church recognises saints much like a country recognises its heroes (think Mashujaa Day) or the NBA recognises its hall of fame stars or FIFA does with the ballon d’or. The Holy Spirit makes saints, the Church publicly recognises as many of them as she can (which naturally will always be a very small percentage).
It’s not the recognition that makes Messi the best player in the world (please note: Messi. Not Ronaldo). It’s because he’s the best player that he can be recognised. So too, its not beatification or canonisation that makes people saints. It’s precisely because they are saintly/holy that they can be beatified/canonised.
Why does the Church recognise the sanctity of people who died a long time ago?
Similar reason to why FIFA and the NBA fete their superstars:
1. First because the superstar deserves it. He is objectively that good.
2. For other players and fans to have something concrete to aspire to.
So too with the Church:
1. The saints are objectively that holy.
2. For the rest of us to have something concrete to aspire to.
But isn’t this some form of idolatry?
It would be idolatry if we gave them worship/adoration due to God alone. But in the same way your mother is pleased when you complement the food she has made, God is pleased when you complement the saints he has made.