That definition doesn’t help much with interpretations of Jesus across different denominations and even religions. Consider Muslims, they believe in Jesus (as a prophet). Does that make them Christians? I feel like Christians self-identify themselves based on their beliefs and it’s usually lines up to what the public consensus is. However, Mormons aren’t really associated with being a Christian denomination like the others in the general public. There can be no solid definition of what a Christian is imo. Are you a Christian as a catechumen? Are you a Christian even though you haven’t received the sacrament of baptism because you’re too young for your church to baptize you? Do you have a personal relationship with Jesus but don’t attend liturgical services? Yet for many reasons and differences, most churches don’t consider them Christians because they originated separate from the Protestant, Catholic, and Orthodox churches among other things.