Christianity is about motivation; and motivation is about what we want, and why.
Motivation is an inner state; and what matters to Christian salvation is our motivation at the time of choice: at the time when we decide whether to follow Jesus to resurrected eternal life.
So long as he wants to follow Jesus, and so long as his reasons for following Jesus are good - then anybody can follow Jesus. It is essentially a matter of personal choice; and if that choice is for salvation, there will be no difficulty about doing what is necessary to make this choice possible.
Therefore Christianity Just Is a very personal and inward matter and directed to ends "not of this world". So; while inferences can and must be made for practical purposes about the motivation of other people; such inferences do Not map-onto spiritual realities.
Historic Christianity was often (usually) contaminated by the demand to make it the basis of social organization: the demand to make supposedly "Christian" institutions and laws as the framework for a "better world": as, indeed, the framework for personal salvation.
Yet, the Fourth Gospel especially, but also the Synoptic Gospels, seem to be pretty clear overall that following Jesus to resurrected eternal life was about a personal relationship and personal choice in relation to Jesus himself.
Therefore, being a Christian is Not primarily a matter of obeying a religious institution, nor of requiring adherence to the dictates of a particular supposedly-Christian social structure (neither of which existed during Jesus's life).
Indeed (as the IV Gospel informs us) Jesus's main arrangement for the guidance of his disciples post-mortally was the Holy Ghost; which Jesus said was directly available to each individual and sufficient to provide all necessary knowledge and direction for those who wanted to follow Him.
In other words; Christianity is not about making a better world. At best, a better world might be an unplanned consequence of personal commitments to follow Jesus.
Instead; Christianity ought primarily to be orientated towards life beyond death.
And Christianity's implications for this mortal life should follow (secondarily) from our motivation and expectation personally (as Sons of God) to participate in the creative life of the post-mortal resurrected heavenly world.