I appreciate Protestantism’s critique of indulgences and other abuses of The Church early on. These critiques made Catholicism and Orthodox Christianity better in response. Much like how the forks of Bitcoin have made Bitcoin better by seeing what would have happened had we gone down a slightly different path.
I also appreciate Protestantism’s point about reading the Bible yourself and not deferring to authority for your beliefs.
The main critique I have of it is that it lacks the mysticism that allows for a real spiritual experience. Being in a Protestant church feels like being in a court room, or city council meeting. Being in a Catholic Orthodox mass with the incense and chanting and all the traditions feels more viscerally spiritual.