A luxury belief is one that seems like a great to those who are well of as a way of improving the lives of those who aren't well off, but the actual implementation is counter-intuitively destructive to the people they think they're helping. Example: Defund the police.

Sell everything and give it to the poor. Seems like a great idea, right? If everyone would do that, everyone would have enough. But there is the Tragedy of the Commons. What if you earned what you built, and the poor do not?

I think most of what people consider Christ's teachings today approach those luxury beliefs. They were tempered with a moral code and feeling indebted to the grace of God, so they were very powerful in moving society forward. But the Christianity of today would be unrecognizable to the Christianity of 150 or 200 AD.

Constantine's solidification of our modern Christian doctrines under Catholicism have been an incredible moral code (Rome threw out Gnosticism, confusing creation myths, other fragmented gospels; simplifying things into modern Essenian/Paulian Christianity). But people are no longer comfortable with the idea of blood sacrifices. They want to expand inclusiveness while disregarding the moral constraints. Without the moral constraints, why would you even need grace.

Old evangelicals and reformed may not like this move to progressiveness in the Church, but it is literally the next logical expansion of the current Christian mythos.