I have my opinions but I will share them by first giving my view of the historical Protestant Reformation which effectively started in 1517 with Martin Luther. A good synopsis of the Protestant Reformation can be found here.
The Protestants, organized under differing sects and persuasions, never did leave the Roman Catholic Church, in my opinion. Yes, they had specific disagreements with Rome and the link I gave you speaks of these. It's a good read!
However, todays Protestants still celebrate Sunday, Christmas, and Easter, effectively keeping the Roman calendar and Constantinian precepts. Todays Protestants range from being very conservative, biblically oriented denominations, to blasphemous far left Satanic denominations. Essentially, ALL protestants are simply protesting Catholics!
Even the Seventh-Day Adventists are still joined at the hip with Rome. They will say they are not, but SDA folk still celebrate the Roman Calendar and Constantinian precepts. About the only difference between a Baptist and an SDA'er is the worship on Saturday rather than Sunday. Another difference would be their teaching of vegetarianism. My wife and I attended an SDA church for over a year and would have joined except when a Pastor asked if we drank wine or beer and we answered, yes - we discovered that SDA is not really that biblical. In short, they wanted nothing to do with us! : )
So, lets talk about the REAL reformations that have occurred in history.
In pre-Christian times, let's say 200 B.C. or better, Judaism was very different than at the time of Christ. By the time of Yeshua's ministry the Pharisees had very much seized control of "Judaism". Judaism had been re-formed into a different mold. The only constant that has remained in Judaism, I would argue, is Torah. This doesn't mean, btw, that Torah has always been obediently observed throughout all of Jewish history; it simply means that "Judah has retained the Scepter and Torah" as Genesis 49:10 states. Today, a myriad of Jewish sects are available; Reform, Conservative, Orthodox, Chabad-ic, Hasidic and even some esoteric denominations based in Cabbalism! Judaism has been re-formed throughout history, for good or ill.
Christianity is similar but I believe it's reform has been more dramatic. When we look at "Christianity" in it's original form it was Jewish in nature and practice. It was NOT Pharisaical, but biblically "Jewish". Torah was observed, Yehovah's celebrations were practiced, and the only Rabbi was Yeshua Himself! In fact, I see early Christianity as a reformed/renewed Judaism. Yeshua knew the Aaronic Priesthood would be suspended and the Melchizedekian Priesthood would rise again to prominence. Unfortunately, most "Jews" ignored what was happening - just like today!
Then a horrendous reformation happened during the next 400 years or so. This change was definitely for the worse. Early Apostolic and Jewish Christianity became horrifically Roman, under the threat of death - Constantine being a true antichrist type if there ever was one! For Christians this was the first REAL reformation.
Later on came the historical Protestant Reformation mentioned earlier which was not really a reformation in a true sense.
What about today? It is my opinion that another REAL and true Reformation is occurring right before our eyes! It is the re-forming/re-newing of the original Apostolic and Jewish centric assembly. Some call it Hebrew or Hebraic Roots. Others call it 1st Century Christianity. But, no matter what label you wish to attach to it, it is a movement of the Ruach Kodesh (Holy Spirit) and NOT a man-made reform! In fact, when men try to claim it as their own they are shunned. A great example of this man-made reform is Messianic Judaism, which is simply another man-made religion and denomination of abomination.
Now, what does all this have to do with the original question concerning Islam? Can Islam be "reformed"? In short the answer is no because Islam is so restrained by men (just like the RCC) that it is immoveable from it's doctrinal pedestal. Islam means "submission" and that submission is brought about by force and not by gentle and loving persuasion as Christianity and Judaism is intended to be.
Does this mean that all Muslims are doomed? Of course not! Our Father Yehovah/Yeshua does not work that way! In fact, the numbers of Muslims coming to Christ is exponentially increasing as we inter-mix and share lives.
Does it mean Muslims will stop the carnage (Ramadan 2019)? No, over 1,000 casualties in the first 3 weeks alone! Remember, how many millions were killed by the Roman Catholic Church over history?
So now, we begin to see the results of bad reform vs. good!
… just a few thoughts ...
The Observer
