The Watchtower conflates two different groups into one fictional Church-Age group that according to the Watchtower, are saved by works and faith/membership in the Jehovah Witness organization. According to Watchtower, only the now mostly dead 144K receive the promises of God regarding Justification . Everbody else missed the boat and must work for their Justification for a thousand years. That is not good news. Thankfully, that is utterly untrue.
When Jesus said that he had other sheep not of this fold, he had already made it clear that he was only sent to the lost sheep of the house of Israel. He later raised up the apostle Paul and others to reach the other sheep among the Gentiles.
Acts: 13 On the next Sabbath almost the whole city assembled to hear the word of God. 45 But when the Jews saw the crowds, they were filled with jealousy, blaspheming and contradicting what Paul was saying.
46 Then Paul and Barnabas boldly said, “It was necessary that the word of God should be spoken to you first. But seeing you reject it, and judge yourselves unworthy of eternal life, we are turning to the Gentiles. 47 For thus has the Lord commanded us:
‘I have established you to be a light of the Gentiles,
that you may bring salvation to the ends of the earth.’[a]”
48 When the Gentiles heard this, they were glad and glorified the word of the Lord. And all who were ordained to eternal life believed.
So, now that we have the "other sheep" identified - Who is Great Multitude?
In Revelation, Jesus gave John a vision describing an immense gathering of people standing in front of the Lamb’s throne in heaven, wearing white robes and joyously celebrating with palm branches as they worship God in a loud voice. Who are these multiethnic, culturally diverse, multilingual people of every nation, tribe, and language? The answer is given in Revelation 7:14: “These are they who have come out of the great tribulation; they have washed their robes and made them white in the blood of the Lamb.” Scripture leaves no room for doubt: these are the ones saved through faith in Jesus Christ during the Great Tribulation.
The "Great Multitude" are NOT Church-Age believers. Church-Age believers have already been raptured (evacuated) to heaven by this time. So, what this means is that the promises of God for full Justification and being claimed by him as one of his sons (or daughters) is still available for "whosoever" that wants it.
Luke 9:48 Whosoever shall receive this child in my name receiveth me: and whosoever shall receive me receiveth him that sent me: for he that is least among you all, the same shall be great.
Luke 12:8 Whosoever shall confess me before men, him shall the Son of man also confess before the angels of God:
John 1: 2 But as many as received him, to them gave he power to become the sons of God,
2. Cor. 5: 21 he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him.
Fully Justified ! (declared righteous)
Now that is some good news.