Let's compare Catholicism to Old Testament Judaism...
OT Jews were the "chosen" people. Catholics believe that they are the "chosen" people and other believers -- God's adopted children -- are not.
OT Jews had a single person mediating between themselves and God. Catholics need the Pope mediating between themselves and God.
There was a separate priesthood in the OT. Catholics have a similar separate priesthood. Protestants have no need for intermediaries between themselves and the heavenly Father.
Forgiveness was accomplished by works (sacrifices) in the OT. Forgiveness for Catholics requires works: penance, prayers, etc.
OT Judaism was centered in one city: Jerusalem. Catholicism is centered in one city: Rome.
The OT Jews conquered indigenous people via warfare. Catholics also conquered indigenous people via warfare.
OT Judaism had, as its center, the temple in Jerusalem. Catholicism has its center as the Vatican in Rome.
OT priests dressed in ornate costumes. Catholic clergy dress in ornate costumes.
Jews confessed their sins to priests, then had to atone by works. Catholics confess their sins to priests, then have to atone by works.
The OT Jews erected a golden calf as an idol to worship. Catholics have many statues (idols) to worship.
The OT Jews worshipped Abraham, Isaac, and Jacob. Catholics worship "saints" (even though all believers are saints).
Jews have the Bar/Bas Mitzvah ritual to declare children as "adults". Catholics have confirmation for the same purpose.
The Jews, until recently, had an all-male "clergy". Catholics have, even today, an all-male clergy.
Jews practice infant circumcision. Catholics practice infant baptism.
The Jews burned incense in the temple. Catholics burn incense in church.
The Jews were divided in 12 tribes. The Catholics revere 12 apostles.
And there are undoubtedly more similarities between the old covenant Jews and the Catholics, but these were just "off the top of my head".
Protestants believe in Biblically-based, New Testament theology, not a reconstruction of Old Testament Judaism.