The position you are arguing for ultimately would suggest that God hasn’t actually told us much of anything. Unless the only thing God is saying is some basic moral precepts. But if that were the case, then the conclusion isn’t that all religions are true, but that all religions are wrong.
Judaism says there is only one God, that God chose Abraham and made a promise to Abraham and to Abraham’s descendants, through the line of Isaac, and then Jacob, to the twelve patriarchs. That promise is kept when God, ultimately, brings the Jewish people out of captivity in Egypt, into the desert of Sinai, at the base of Mt. Horeb, and hands down His Torah. God then brings His special people, Israel, into the land of promise, and establishes them as a nation there. The entire Jewish religion insists on God having done very specific things. Now, Judaism does not claim that non-Jews must observe the Torah, as Torah is only for the Jewish people. Judaism does, however, maintain that righteousness among the nations depends on recognizing the same and only God of Israel, and living according to more general, universal commandments, such as not to worship other gods, not to worship idols, not to engage in certain behaviors, etc. So there is a universal quality of God’s expectations for all humanity, and a special covenant with the Jewish people.
Now, say, let’s look at Islam. According to Islam God reached out to a man, Muhammad, and over a period of time, through the angel Gabriel, revealed what would later be written down as the Qur’an. The Qur’an is God’s Revelation (capital ‘R’) to the whole world. And so Muslims are required to affirm the Shahadah, “There is no God but God, and Muhammad is his Prophet”. Further, according to the revelations given to Muhammad as recorded in the Qur’an, many prophets came before, such as Adam, Noah, Moses, and Jesus–but these are all inferior to Muhammad. And the revelations given through previous generations of prophets have been distorted over time. Muslims, therefore, believe that while God did choose Abraham, it was not through the line of Isaac, but of Ishmael. And that while God did reveal His Torah through Moses, it has been corrupted. And likewise Muslims believe that King David was a prophet, whose work of the Psalms were a revelation that became corrupted. And Jesus came, as a prophet, with a work of prophecy, the Gospel, which was corrupted. If Islam is true, then Judaism is not true. The two cannot be equally true. Because there are exclusive claims each religion makes.
When we, then, speak of Christianity. Christianity argues that God chose Abraham, and the promise was through Isaac, through Jacob, and to the twelve patriarchs and thus tribes of Israel. What the Jews call the Tanakh, Christians know as the Old Testament, and also hold that it is true. But Christians maintain that the promised Messiah is Jesus. Judaism doesn’t acknowledge Jesus as the Messiah, but says the Messiah is still yet. Even still, Muslims do agree that Jesus is the Messiah. Christians say that Jesus is not only the Messiah, He’s the Son of God–He’s God Incarnate. And that Jesus’ life, death, and resurrection are God’s act to redeem and save the whole world. Jews, obviously, don’t recognize Jesus as anything–Jesus is irrelevant in Judaism. Muslims acknowledge that Jesus was the Messiah, even that He was born of a virgin. But deny that Jesus is the Son of God, they deny Jesus’ Divinity, they do not believe Jesus even died on a cross, instead that Jesus escaped death altogether, but was taken into heaven without dying. Jesus will, when He comes again, according to Islam, die and rise from the dead as part of the general resurrection. Christians, additionally, reject the claims of Muhammad of being a prophet. Christians regard Muhammad as a false prophet, and the Qur’an as an un-inspired text that is entirely irrelevant to us. In the same way that Jews consider the New Testament entirely irrelevant to them.
And here we are dealing with just three religions, religions which share a LOT in common actually. And yet with claims which are mutually exclusive. There’s simply no way to reconcile those differences without completely destroying all three religions. If one says “Judaism, Christianity, and Islam are all true” that isn’t actually helping anyone. That’s actually saying “They’re all wrong”–because the deep faith claims each religion makes are only true if they are specifically true. Jesus can’t be the Messiah AND not the Messiah at the same time. Muhammad can’t be a prophet and NOT a prophet at the same time. Isaac can’t be the chosen son and NOT be the chosen son at the same time. The New Testament can’t be true and NOT true at the same time. The Qur’an can’t be true and NOT true at the same time.
And this isn’t even touching on the many other religions that exist in the world: Buddhism, Jainism, Sikhism, Shinto, Wicca, just to name a handful.
While the desire for mutual peaceful co-existence among people of diverse and different religious persuasions is a good one. And it’s one I think we should seek to have in our pluralistic societies which we have established in the modern world; where religion is not imposed by the State, and no religion is oppressed by the State. The means to do this is not to say “all religions are true”, because that’s actually deeply insulting to ALL people of faith. It’s insulting to Jews, Christians, Muslims, Buddhists, Jains, Wiccans, Sikhs, and all many other religious people. Because it is actually saying, “What you believe doesn’t matter, and you’re actually wrong–but I’m going to pretend as though I’m not dismissing your more cherished and strongly held convictions about the universe”. It’s not kindness, it’s bigotry under a different form.