Is it really so that only those going to heaven should partake during the memorial of Jesus Christ's death?

You're attempting to determine literal meaning from Revelation, which is symbolism through and through.  It's a fools errand, neighbor.

NO ONE GOES TO HEAVEN, man's place is on the earth.

The website (below) states that there are between 14 million and 24 million Jews in the world. Of that number, the bible says 144,000 will go to heaven, representing 12,000 from each of the extant 12 tribes. Ethiopian Jews (according to several websites below), known also as Falashas or Beta Jews, are most likely Christians who converted to Judiasm with Black, Ethiopian (non-Jewish) fathers as shown by their Y-chromosomes. Therefore Ethiopian Jews are not of any of the 12 tribes of Israel. The ancient wealthy Kingdom of Kush, just south of militarily strong and aggressive Egypt, was militarily weak, but their wealth kept Egypt at bey. Of course the 144,000 figure is from Christian sources (New Testament), not from Jewish sources (Old Testament). The Old Testament indicates that all Jews will go to heaven. Perhaps the New Testament was written to get Jews to convert to Christianity?

Re: Rev. 7, 14. Points to consider: Tribe of Dan omitted. "Tribe of Joseph" added. (There was no tribe of Joseph) Manasseh included, but not Ephraim. If chapters 7&14 are literal, only unmarried Jewish men are included, "who did not defile themselves with women". If the 144,00 is literal then the "lamb" in that context is also literal. Figurative language allows for these details, but to be literal there must be no contradictions, no impossibilities, and no absurdities according to the "sense" of the passage.

1) Is it really so that only those going to heaven should partake during the memorial of Jesus Christ's death?

No. See: Paul's letters.


2) First off, think about Revelation chapter 7. This scripture is talking about the 144,000.

...and several other things.


3) Now think about it: these were taken out of the twelve tribes of Israel.

Twelve of the thirteen tribes of Israel
and
the names given for those twelve tribes is...odd.
Joseph included?
Ephraim and Dan omitted?
Probably there is some significance.


4) So, then, there are those who are still considered of the twelve tribes of Israel. But are not part of the 144,000. Next, think about this: when Paul spoke about those partaking unworthily in 1 Corinthians 11:27, who was he talking to?

Christians who were dishonoring the ritual of The Lord's Supper.


5) Were there any of those not going to heaven involved with this statement? John, in Revelation 7:13, 14, when asked who these of the great crowd were, he didn't seem to know when he said "Lord, you are the one that knows". It doesn't seem like Paul was saying these who were unworthy of partaking were unworthy because they were not going to heaven but that they were not worthy because they had not become part of Abraham's seed in their hearts, which is what Paul was talking about in Romans 2:28, 29.

See 1Co 11.
Paul explains.
Christians were gathering to eat and drink, calling it "the Lord's Supper", and were "jockying for position" to be first in-line to get their grub and wine.
Paul condemned them for this (unworthy) practice
instructed them to eat at home if they were hungry
and instructed them to gather not to eat a meal, but to celebrate the Lord's Supper.


6) Now, think about this: who of Israel were supposed to partake of the lamb of the Passover? Was it not all of them?

All Israelites.


7) So, since not all of spiritual Israel are part of the 144,000 and all of Israel are supposed to partake, should not all of those spiritually inclined as part of Israel partake? Now, I know what you might be thinking: Jesus concluded a covenant with those partaking (Mt 26:28). Well, think about who benefit from Jesus Christ's blood? Is it only those going to heaven? Well, consider what John 3:16 points out. Jesus' blood was for all those who exercise faith in Jesus.

What are you talking about when Jesus said "I will not eat  with you anymore until it's FULFILLED in the Kingdom of God" (Luke 22:16) and "I will not drink of the fruit of the vine, until the Kingdom of God shall come" (Luke 22:18)?

You don't know "The Kingdom of God" 

>>>CAME<<< 

On the Day of Pentecost (Acts 2:2-4)?

Jesus said in Matthew 12:28 

"But if I cast out devils by 

>>>THE SPIRIT OF GOD,<<<

THEN

>>>THE KINGDOM OF GOD<<<

is come unto you."

Consequently The Kingdom of God is the Holy Spirit who >>>CAME<<< on the Day of Pentecost

AND >>>FULFILLED<<<

>>>SETTING UP TABLES<<< (Heb 9:1-2)

As we NOW >>>EAT SPIRITUALLY<<< 

as did our "examples" (I Corinthians 10:11)

Who "Ate Spiritual meat and drank Spiritual drink" (I Corinthians 10:3-4).

"UNBELIEF" (Malachi 2:2-4)?

HENCE

>>>CORONAVIRUS!<<<

No, John, none of that is 'really so'. It's entirely fictional religious mythology. Were you more capable of critical thinking and judgment, you would have realized that without asking.

The fact of the matter: The 144,000 thousands all came out of the church age, but there will be a great multitude that no man can number read Revelation 7:9-17