I keep returning to this problem at the root of Christianity as it is usually observed and defined...
In the second part of the Fourth Gospel there is a great deal about the need for love as the core of how we should be, and about the very specific love between Jesus and certain specific people - members of his family; Lazarus, Mary and Martha; and the disciples. This is love in a context of intense, prolonged, personal relationships - often between familially-related people
The problem is then scaling-up this personal love. Most Christian churches instruct their members to love everybody; and there are frequent 'claims' of love between those within the church. I know such claims are familiar to the point of stereotypical; but I doubt whether this is even possible (in the same sense that Jesus meant love).
And if it is Not possible really-and-truly 'routinely' to up-scale love from family and close friends, to a specific church, to a denomination, to all Christians, to all the world... then this is a very serious dishonesty or error at the heart of the institutional and social basis of what has usually been termed Christianity.
The love that Jesus spoke-of and lived in the Fourth Gospel seems like a very different thing from the love discussed (as an abstract idea) by so many Christians since that time.
If real love operates at this familial-friendship scale; then real Christianity may be an almost invisible and imperceptible thing. It is possible that most real Christians (followers of Christ) lived and died unrecorded, unknown to history - or even to the people among whom they dwelt.