When a quality complex product is being engineered, it requires exacting specifications and details that must be fulfilled in order for it to work properly. Likewise of the measuring up to being among the "few" who will find "life" requires that they measure up to God's holy (high) standards.(Matt 7:14) Most who profess to be "Christian" never delve into the details of what is required to gain God's favor, but just "beat around the bush". Some use the cliche "Believe on the Lord and you will be saved" to support their ideology.
Jesus established that the vast majority of mankind will soon perish, saying: "Go in through the narrow gate, because broad is the gate and spacious is the road leading off into destruction, and many are going in through it; whereas narrow is the gate and cramped the road leading off into life, and few are finding it."(Matt 7:13, 14)
This vast majority includes the churches of Christendom, for they are the ones that have told falsehoods about our Maker, Jehovah God, with such erroneous doctrines as the Trinity (supposedly God is three persons in a "Godhead"), hellfire (making God to be a fiend who burns wicked people everlastingly for their sins), immortality of the soul (saying that this is "something" that separates from the body when we die), profaning God's name of Jehovah by either making snide remarks about it (that since we do not know the correct pronunciation, we should stick to "God" or "Lord" ) or hiding it from others (as the translators of various Bibles have done by supplanting Jehovah with "God" or "Lord"), of creating a clergy class that elevates itself above the common people (using such titles as "Reverend", Monsignor [meaning "my lord"], Pope (meaning "papa", etc), making themselves "a god".(2 Thess 2:4), use of the cross.
Jesus pointed out that there would be those who would even be very religious in our day and say: "Many will say to me in that (or our time period) day: ‘Lord, Lord, did we not prophesy in your name, and expel demons in your name, and perform many powerful works in your name ?’ " (Matt 7:22) But instead of praising them for their so-called "Christian" activities, rather Jesus says: "And then I will declare to them: ‘I never knew you ! Get away from me, you workers of lawlessness !’ "(Matt 7:23) Jesus sternly condemned them. Why ?
Because these set their own personal "Christian" course, establishing their own teachings (even when from pagan sources) or making Christianity like a buffet, choose what they want and throw the rest away. For example holidays. How much effort does it take to recognize that Christmas is not based on the Bible or that Easter has a pagan origin or that Halloween delves into the wicked spirit realm ?
In reality, not that much, but many keep on celebrating them without question because they reason that Christmas is "a good time for families to get together" (and "everybody else among the churches is celebrating it") or that at Easter, they can wear some new clothes to church or that Halloween is just "fun time".
These perhaps never sit down and reflect on 2 Corinthians 6, that says: "Do not become unevenly yoked with unbelievers. For what fellowship do righteousness and lawlessness have ? Or what sharing does light have with darkness ?" (2 Cor 6:14) These never seriously think about Paul's words: "Therefore, get out from among them, and separate yourselves,’ says Jehovah, ‘and quit touching the unclean thing ’”; “‘and I will take you in.’” (2 Cor 6:17)
These do not give serious thought to what pleases God, what is "righteous" as opposed to what is "lawless". These do not somberly look for information that shows the pagan origin of Christmas (of it being a Roman celebration called Saturnalia [from December 17-24] and that December 25 was the day the Romans celebrated the birthday of Mithra [Persian god of light] as the "invincible sun"), that the day of Jesus birth is not mentioned in the Bible (but that the Bible gives highlight to "the day of one's death" at Ecc 7:1), as well thinking carefully about Easter as to why it has rabbits and eggs (as well as recognizing that Jesus taught his disciples to observe his death, not birth nor resurrection, Luke 22:19, 20; 1 Cor 11:24-26) or that Halloween is a day (or night) that brings out "witches and ghosts and goblins" and say: "Hey, these all have pagan origins and I need to get rid of any association with them."
Thus, Jesus, in telling his genuine disciples to be "no part of the world" (John 15:19, having three main entities - 1 - false religion, 2 - greedy commercialism, 3 - and dirty politics)", says to these so-called "Christians": "Why, then, do you call me ‘Lord ! Lord !’ but do not do the things I say ?"(Luke 6:46) Thence, only a "few" are willing to clear away all false religious doctrines, to be free of greed and have no participation in the political arena, "bringing every thought into captivity to make it obedient to the Christ."(2 Cor 10:5)