I've watched religious identity get weaponized in political conflict in ways that felt like it betrayed the actual spiritual heart of what faith is supposed to be about, and full separation feels like the only way to protect religion itself from being used as a tool of state power.
Countries like the UK maintain an official state religion, with the Church of England's bishops sitting in the House of Lords, while consistently ranking among the world's most religiously tolerant and free societies -- showing some formal overlap between religion and state doesn't automatically undermine broader religious freedom in practice.