True, we can’t judge individuals. We don’t know their upbringing, experiences, knowledge, temptations or what spiritual insights graces they have received. The individual who is in Jehovah’s Witnesses may be a better Christian than I am. There are other groups even farther removed from the Catholic Faith with Christian individuals.
The Catholic Church has a term, “ecumenism”, for relationships among Christian faith communities. The Church has another term, “interreligious”, for relationships among Christian and *non-Christian *faith communities. This includes groups that self-identify with Christ, but whose doctrines and practices are now moved so far from Catholicism, the Church no longer regards them - the organizations - as Christian, though they previously were so included. This does not judge the individuals but the church as non Christian.
RC bishops meet with local Anglican and Mormon leaders. They try to build common ground wherever possible. It may be that the Mormon church in one country may be coming closer to being a “Christian church”; perhaps they now omit certain doctrines incompatible with Catholicism and become trinitarian. There was a cult founded by Herbert Armstrong that has since embraced standard evangelical doctrines. Change can happen in both directions.
or,
It may be that the Episcopal Church, or a given diocese, is now so far removed from Catholic Faith that it is no longer a Christian church. I would argue some mainline denominations, farther along than TEC, have abandoned Christianity; one of them is introducing new gospels into the canon of the NT. TEC has not done that.
One can argue the TEC has not yet crossed that boundary. But it is moving, and there is a boundary.