Mainline Protestant churches have female priests and bishops, whereas Rome and the East have none. Mainline Protestants have more openly embraced LGBT immorality, the major exception being Evangelicals, but that is beginning to change. Of course, there is liberalism and degeneracy in the Roman and Eastern realm, but it doesn’t seem as bad as Protestants. This perhaps can be debated, but let’s grant the point. There are faithful Protestant remnants, but they are just that, remnants.
Two thoughts.

1. In the Great Divorce, C. S. Lewis speaks of natural affections and natural appetites. He says that natural affection can be more easily led on to eternal love than natural appetite can. But it can also more easily stop short of that end, which can make it more dangerous. He says, “It is a stronger angel, and therefore, when it falls, a fiercer devil.” I think this can be applied to Protestantism. It is a stronger angel. God graced Protestants with First World blessings, wealth, and power, for example. Something we see as the result of covenant faithfulness in Deuteronomy 28. But we have broken covenant, and so are given over to curses, and have become fiercer devils as a result.
2. When St. Peter sees Jesus walking on water and hears our Savior beckon him, St. Peter walks on water to the call of Jesus. He follows Christ in a miraculous moment. This, to my mind, is like Protestants, willing to follow Christ no matter what. And when St. Peter took his eyes off of Christ and gave in to fear and doubt, he began to sink into the raging sea. This is Protestantism now. Having given in to fear and unbelief, we are being overcome by the waves of the world. The rest of the disciples, representing Eastern Orthodoxy and Roman Catholicism, never pursued Christ in that manner and so remained dry and safe in the boat. St. Peter cried out to Christ to save him, and He did. If Protestants cry out to Christ once again, repent of their fear and doubt, we will once again walk on water.