To me, the central issue is unsolvable. And I mean that. Every religion has its issues.
- Judaism has a huge problem with the issue of halakah: those Jews who believe in following the rules (600+) that have been gleaned over the centuries from the root text versus those who to varying degrees don't. This results in schisms over what God wants, desperate arguments over who is entitled to be a Jew, claims by the devout that their study so pleases God that it insulates Jews from harm, blame by the devout that failures of other Jews to be devout enough brought about the Holocaust, denial that Israel can exist, increasing insistence that non-observant Jews follow the codes of the observant, etc. The less observant (of varying degree) Jews believe in a form of Judaism that looks more to substance, that sees God's interest in human affairs differently, etc. Big problem, entirely focused on Jew versus Jew. It comes out in the Israel/Palestine conflict as the hard right and religious settler fringe who see Jews living in Judaea and Samaria as necessary, both to bring about redemption by God and as acts which insulate Jews from God's wrath. Not only are there not that many Jews, but despite fantasies about Jewish world domination the scope of this land obsession essentially reaches to the Jordan River. I think this limitation reflects how old Judaism is and thus how intimately it is linked with specific places rather than to a globe that no one then knew existed.
- Christianity's big problem is that it claims - alone of the major religions - to be the exclusive path to God. Two big lines in the theological book of John written decades after Jesus ... but there they are. This has led not only to the Christian need to convert but to the patronizing way Christianity treats other religions: they are lesser because the only path to the Father is through the Son. No matter how many Christian sects exist, there is always this tendency to see Christianity not only as "my religion and thus the best religion" but as the "only true religion". This has been a huge factor in the deaths of many, many millions around the globe. Example: Christian wars between two groups claiming to be the one true religion have killed tens of millions of Christians in Europe, with one of my favorites being a French Bishop's letter describing how in the name of Christ they put the Protestant families on rafts, tethered them in the middle of the river and set them ablaze. (He used nearly the exact words Rudolf Hoss used when "defending" his mass executions at Auschwitz!) Because Christianity is born back to "only", it has great trouble seeing other religions, even other people, as they are rather than as those Christians need them to be. Or as Sartre put it, it is the anti-semite who makes the Jew, meaning he constructs what he thinks the Jew must be even though the Jew is not that way. (It means more generally that even highly educated Christians know almost nothing about a) Judaism and b) how their view of Judaism, Jewish belief and practices is distorted and c) how completely they interpret Jesus et al without reference to their Jewishness.
- Islam has two big problems and they connect to make our current mess:
A) First is that the Quran claims repeatedly to be a book without doubt and without ambiguity. No matter how educated, how “Westernized”, many Muslims are drawn to the literal word of material that dates back to the 7th century. By contrast, even the most devout Jews believe in the Oral Law: that along with the Written Law, God handed down Oral Law that we must figure out. (That is what the devout study: not memorization but meaning and what ideas can be gleaned, how much evidence can you find to support your idea, how well does it fit into historical interpretations, etc.) There are of course Christian fundamentalists who believe in the literal word of the Bible and maybe one day they will attain prominence but demanding literalness hasn’t been the main Christian trait (and it’s been a few hundred years since Christian scholars started to examine Biblical origins). I think the difference is that Christianity sees itself as trying to be Christ-like through parables and lessons that attempt to illustrate the ideas of a Christ, while Islam sees itself as devotion to a remote God (who sounds much like the Jewish God) through the literal words of God’s prophet. In other words, Christians treat the guy Jesus as avatar God and Muslims treat the guy Muhammed as the Prophet of the much greater God. It’s really tough to overcome being drawn into the world of the 7th century, especially when there are direct words (as in you need 2 women to testify, etc.) and the examples of the Prophet (who isolated his women and married more than 1) and “hadiths” and lesser sayings attributed to people who knew Muhammed and which are more or less treated as non-Quranic words of the Prophet.
b) Second is that Islam also claims to require, not just think desirable but require, submission of the world to God’s word. It isn’t that Islam is the only - the Quran repeatedly said God loves good Jews & Christians - but a different form of “only” in which the world can have more than one religious belief as long as Islam rules over them. That is actually somewhat of an Old Testament notion: the God we call “God” is often referred to in the Torah in the plural and as one “name” among many and the 2nd Commandment (after I am the Lord your God as #1 in Judaism) literally says you shall have no Gods before me, which is a rather blunt statement that there are others but you must believe in me as the top God. Islam extends this from what the Quran calls “the people of the Book” to all people: Judaism doesn’t care what others believe at all in any way but Islam cares that its God be #1 for everyone, that non-Muslims accept their status under Islam (or be enslaved or killed). As a side note, the horrors visited upon Yazidis and others (Ahmadis in Pakistan, Shia versus Sunni generally) is because they are considered heretics and those are much, much worse than non-believers.
Maybe in some hundreds of years Islam may move past its twin core problems of being drawn deeply into a pre-modern, pre-rational past and of demanding world control but I think it’s just as likely the world moves into that darkness.
The usual disclaimers: I’m talking about groups not you. You may be an observant Jew/Christian/Muslim and feel nothing but love for people and disgust at stupid hatreds and violence. Indeed, I would add that the largest volume of Islamist propaganda is aimed at shaming and threatening other Muslims: they risk being declared heretics for participating in the West, for not actively taking steps to overthrow the West so the reign of Islam may be established, for not working to remove other heretics. This is absolutely on purpose; it aims to cajole some, enough to act whether out of both active devotion or fear of God’s wrath or fear of having their own heads cut off.