This is restating the argument of my post of a few days ago - from another angle.
There are many Christians of many types - if we take the definition of those eligible for resurrection to life eternal (1) a follower of Jesus who (2) acknowledges his divinity - which is what Jesus says, repeatedly, throughout the Fourth Gospel.
Among those who style themselves Christian in the modern world, there are many who - By My Judgement - are not Christian. This could be termed the 'Fake Christian Crisis' - it is the infiltration of all Western Christian churches by Leftists and Sexual Revolutionaries - aiming incrementally to subvert, destroy, take-over, and invert most of real Christianity. Fake Christianity has replaced all, or nearly all, of the leadership in major Western denominations including Roman Catholics, Episcopalians, Methodists, Presbytarians and most mainstream evangelicals.
And - also By My Judgement, and according to the Fourth Gospel definition - the real Christians are scattered across many churches denominations and no denomination-at-all.
This is 'easy' for me to assert, since I am in the no-denomination category (although associated with, supportive of, a Church of England Conservative Evangelical church); but, since Christians are in a shrinking and persecuted minority in The West, almost every real Christian wants (as I do) to be able to ally-with/ work-with other real Christians.
But... this become de facto impossible when the real Christians respond to the Fake Christian crisis by doubling-down on the legalism. In a nutshell, the strategy is to define the Leftist Sexual revolutionaries as heretics, and to exclude them on that basis.
But the real problem is not heresy but apostasy - the Fake Christians may be orthodox in narrowly defined legalistic terms, they are usually prepared to stand up and make strict oaths and promises in which they do not believe and have zero intention of living-by; but they are Obviously Not Christian in terms of not being followers of Jesus and/ or not believing in the divinity of Jesus.
This is presumably why the legalistic approach to fighting Fake Christianity has been a near-total failure.
What can easily be seen by the truth-seeking and discerning eye (or rather heart) is typically invisible to the words of legalism. The answer is simple, but it depends on honest, informed human judgement - for which there is no substitute - nor will there ever be a substitute... so long as Goodness is required: Goodness is a personal, not abstract, attribute.
Once we have cast aside the false idea that Christianity is, or ought to be, protected by legalism - by definitions and procedures (surely an idea that would have been rejected - sharply - by Jesus?) then matters can be much clearer - clearer although not, of course, necessarily easy or simple in practice.
For this to happen each must take personal responsibility for the judgement that he or she must make about others: we must judge others, and we must also be clear that the judgement of others is, can only be, must be for each of us - a personal judgement.
That is to say, we each must discern (with the discernment of the heart - not by checklist and tickbox) who are the real, and who the fake, Christians - and act accordingly, And 'must' means must.