It is impossible for the Church to change her doctrines. Develope, yes. Change, no.
"develope" is a form of change. ( it is)
Priests weren´t always supposed to be celibate, then they were. Infalibility wasn´t a doctrine until some "Pio" pope. then it was.
Ironically, the same pope that preached infalibility was judged by his peers to be mentally unstable.
There are letters of people of their time (priests) stating this. There was a time this "infalible" Pope wanted to use his "infalibility" power and ordered an incapacitated person to walk. The incapacitated person tried... and failed.
A lot of popes said infalibility was a lie that was inspired by the devil. This is because the "infalibility" of the statements of the last Pope didn´t let them make contradictory statements, thus undermining their authority. So a lot of Popes were against infalibility for this very reason.
Infalibility is a ridiculous doctrine.