I find this topic more and more interest after encountering Catholic/Orthodox theology, because they have no sense of discerning visible and invisible church, nor would they want to.
So in the Invisible sense of the Church, no true Christians would leave the Church, because that would mean abandoning Christianity.
However in short, in the visible church, because it's a visible one, it's one in this world, it's one that is prone to falsehood, leaving such churches is sometimes not only allowed be required by God.
The calling by God to do so, would really be up to the subjective conscience instead of a universal principle. However, if God's name is invoked in such manner, the criteria for such decision is only one: That it hinders the work of God, the Kingdom of God. It cannot be because one doesn't feel welcomed, or there's not enough youth programs, or there's not enough free food to go around, etc.
Such has been the case I've made for when we decided to leave a church. By leaving, I don't mean when someone immigrated to another state. I do however mean either a disassociation or seeking for a church where God's Kingdom is truly seen and clearer than the previous ones.
So when one moves from a Baptist church to a Reformed one, or even vice versa (For many Reformed churches are not really reformed anyway), it is possibly appropriate. We left CCCNY because Rev. Laura Lin cares more of men's than of God's. We left MERF of NYC because Pastor Paul Murphy's church is more tribal ("If you're not going to be a member I have no obligation to fellowship with you") than heavenly. We left Westfield OPC because Pastor Tim Ferguson's church is also more tribal (My church/family is God's Church/Family) than heavenly (God's Church/Family is my church/family).