Well, I think Luther’s actions should first be understood and doing that requires acknowledging certain realities about the state of the Catholic Church in Luther’s time. The Church had plenty of inquisitors to police the laity, but there really wasn’t any oversight of the clergy or religious and they ran amok. Rome was indifferent so if your local clergy or religious said, did, or promoted things that were in flagrant violation of Catholic doctrine then that was your problem. One of the obvious issues being that there was a rather large class of poor and uneducated people who couldn’t tell the difference, relied on their local clergy and religious to tell them what they needed to believe, did what they were told out of obedience. The corrupt preyed upon that dependency and the roots of such issues as simony were vast and deep.
Those two things were the very heart of Luther’s objections. The reformation was not about separation, but intent to reform the Catholic Church to enforce its own doctrines and bring the clergy and religious into compliance with them. Rome had no intention of doing so at that time so this led to Luther’s ultimate conclusion, which was/is really the source of contention between Catholics and Protestants. In Luther’s view, it was not enough for Rome to simply repeat Catholic Doctrine. If the shepherds abandon their flock to the wolves, and/or stand implicated of corruption and abuse themselves, and if they treat Doctrine and the Gospels as effectively nothing more than words on paper that don’t require daily living then they have ceded their authority. As he bluntly put it, “Personally I declare that I owe the Pope no other obedience than that to Antichrist.” In the end, if all they’re going to do is enjoy the trappings of their office and use the Church to improve their own lot in life then they are owed nothing.
Asking (more-so demanding) that Luther align himself with a Church that was not aligned with itself was a futile endeavor. I think if Luther were alive today he probably would not leave the Catholic Church because it is in a far better state. There are avenues for recourse to address errant clergy and religious that yield results and there are forums for theological debate. As for whether Luther should have simply forgiven and moved on, well, I wonder what any living Catholic would do if the Church had the same problems today that it did in the 16th century and to the same extent.