We would not be purified in Purgatory unless God made it so. So those who believe in Purgatory do not deny that God alone can make them worthy. The concept of Purgatory says that God allows the souls to be purged of their attachment to sin before they enter His presence.
Mat 5:20For I say unto you, that except your righteousness shall exceed the righteousness of the scribes and Pharisees, ye shall in no wise enter into the kingdom of heaven.
We can not be hypocrites like the scribes and Pharisees.
Mat 7:21Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father who is in heaven.
We can do the will of the Father.
Mat 18:3 and said, Verily I say unto you, Except ye turn, and become as little children, ye shall in no wise enter into the kingdom of heaven.
We can turn and be as little children.
Basically, if we believe and have faith in Jesus and what He did for us on the cross, and accept Him as our savior, and repent of our sins… we are saved and will be able to enter heaven. Because no one comes to the Father except through Jesus.
Gal 2:16 Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified.