If, in fact, the Holy Spirit is God, then we cannot limit how and to whom He will manifest himself. In other words, we cannot say “Holy Spirit, you cannot move through a non-Catholic, non-Catholic church, or even a non-Christian.” In the Bible, we see clearly that God can and does use any number of people with any level of connection to Him, from none at all to totally united, to accomplish His will.
That said, we CAN and SHOULD point out that it is impossible for EVERY different group to be guided by the Holy Spirit BECAUSE of the different theological positions. It is IMPOSSIBLE for Baptists to be correct that infant baptism is wrong and Lutherans to be correct that it is quiet proper at the same time.
For valid orders, one must start with how the Church is to be organized. It does not matter HOW you see the Rome vs. Orthodoxy issue, but both groups hold that the key authority in passing along valid orders is the BISHOP. Luther was not a Bishop, and as a priest, he could not confect valid orders. We should end that conversation there, as it will derail the thread quickly into who does and does not have valid orders.
I am not Protestant for the same reason that I am not EO. Simply put, I do not see more merit in their positions than in Rome’s.