I am very much a doubter, at least as far as the nation of Israel - earthly Israel - is concerned.
But there are two Israels mentioned in scripture, not one: 1) the earthly kingdom of Israel and, 2) spiritual Israel. The earthly kingdom
of Israel is no longer God's wife - God divorced it for spiritual fornications and therefore it is no longer is the object of His blessings - although certain residual parts of God's promises may remain in effect for a while but eventually will end. The other Israel - spiritual Israel - the true church - is the bride of God and the one having God's eternal blessings. Scripture does not always make clear which is in view, so it must be surmised relative to context, subject, and by comparing spiritual with spiritual. Generally speaking, though, if God's eternal blessing is being discussed relative to a nation, then spiritual Israel is the nation in view.
Regarding the twelve tribes mentioned above, they represent spiritual Israel, not earthly Israel. This can be seen based upon the following verses. You will need to read them closely to follow their message.
Notice in them, that only the saved can sing the "new song" - those with the Father's name in their foreheads. The hundred and forty and four thousand therefore is a symbolic number that represents all of the saved, so, it is not a literal number. Only the "redeemed of the earth" could learn the "new song". The "new song" that only they can "sing", is the belief of the true gospel.
[Psa 149:1 KJV]
1 Praise ye the LORD. Sing unto the LORD a new song, [and] his praise in the congregation of saints.
[Rev 5:9 KJV]
9 And they sung a new song, saying, Thou art worthy to take the book, and to open the seals thereof: for thou wast slain, and hast redeemed us to God by thy blood out of every kindred, and tongue, and people, and nation;
[Rev 14:1, 3 KJV]
1 And I looked, and, lo, a Lamb stood on the mount Sion, and with him an hundred forty [and] four thousand, having his Father's name written in their foreheads. ...
3 And they sung as it were a new song before the throne, and before the four beasts, and the elders: and no man could learn that song but the hundred [and] forty [and] four thousand, which were redeemed from the earth.