the catholic church has always been corrupt
I read the Martin Luther biography by Eric Metaxas last year - "corrupt" is too gentle a word.
Man has always been corrupt. No institution is exempt.
The Body of Christ is corrupt? On earth, it is full of sinners, like any other human institution . Currently, it is the subject of an unprecedented attack by Satan.
The Catholic Church, like your church (whatever it is) or any church, is composed 100% of sinners, chosen by God as his faithful, fickle, falling and rising people.
Obviously, that is not the same as saying the Catholic Church has always been corrupt.
I'm on my parish RCIA teaching team (teaching adults who are being received into the Catholic Church). I'm the one who always gives the lesson on Church History.
Having to figure out how to fairly outline 2,000 years in approx. 100 minutes (that's sprinting along at about 20 years per minute, if you want to look at it that way) I pretty much use Christopher Dawson's outline of 6 great cycles of Catholic history, each going from faith to triumph to pride to corruption to downfall, and each lasting roughly 300 years (give or take a century.)
I add a 7th period locating us in a phase of corruption, to be followed by catastrophe, repentance and a renewed walk with the Lord.
The details o the outline may be fairly be disputed, but I think the overall pattern is like that of Biblical Israel. The Lord leads His bride through the wilderness. He will always be there to save.