My Brother sent me the following, about the mark of the beast:

The receiving of the mark of the beast will involve worship.

Also, those who receive the mark of the beast will spend eternity in the lake of fire.

The Scriptures could not be more clear:

“And he had power to give life unto the image of the beast, that the image of the beast should both speak,

and cause that as many as would not worship the image of the beast should be killed.

And he causeth all, both small and great, rich and poor, free and bond,

to receive a mark in their right hand, or in their foreheads:

And the third angel followed them, saying with a loud voice,

If any man worship the beast and his image, and receive his mark in his forehead, or in his hand,

the same shall drink of the wine of the wrath of God,

which is poured out without mixture into the cup of his indignation;

and he shall be tormented with fire and brimstone in the presence of the holy angels,

and in the presence of the Lamb:

And the smoke of their torment ascendeth up for ever and ever:

and they have no rest day nor night, who worship the beast and his image,

and whosoever receiveth the mark of his name.”

My reply was:

The sentence before the mark is mentioned, says that the image of beast is going to cause those who do not worship the image should be killed.

Being killed is a far greater influence than not being able to buy or sell.

So, when people teach that the threat of not being able to buy or sell is to force people into taking the mark & thus guaranteeing their part in the lake of fire.

However, before the mark, people are threatened with being killed, in order to worship the image.

That threat is far scarier to people than not being able to buy or sell.

Anyway, the third angel points out that not only the taking the mark of the beast leads to the lake of fire,

but also worshipping the beast's image leads to the lake of fire, too.

So, if people are more threatened by being killed, than not being able to buy or sell,

then they will have already succumbed, and worshipped the image, by the time the mark shows up,

and are already heading to the lake of fire, so why wouldn't they also take the mark as part of the worship they already began?

Then, those who refused to worship the image, even when threatened with being killed,

if they haven't been killed yet, by the time the mark comes, why would the lesser threat of not being able to buy or sell,

scare them into taking the mark, when the threat of being killed hadn't scared them into worshipping the image?

Also, there are those, now, who are saying that the vaccine is the mark, and will send people to the lake of fire,

and that it will even be forced on people, without their consent, but still condemning them.

That is really wrong, like hyper-Calvinism, saying that those people must go to the lake of fire with no choice on their part.

There is no beast at the moment, so what is the mark of the beast for a beast that hasn't shown up yet?

Also, as you put it, it involves worship, and there is no worship aspect with the vaccine.

I've wondered if the threat to not buy or sell without the mark, or the threat to be killed for not worshipping the image,

is not a threat to force lost people to do it, as they will already have been worshipping the beast (see line 4),

but that the threats are to "smoke out" people who believe in Jesus.

Revelation 13:4 And they worshipped the dragon which gave power unto the beast: and they worshipped the beast, saying, Who is like unto the beast? who is able to make war with him?

People will already wonder after and worship the beast.

The threats, later in chapter, then seem less about coercing worship, which will already have been freely given,

but rather to maybe expose those who do not worship the beast, or who will not worship him.

When people  saw Jesus:

Isaiah 53:2 For he shall grow up before him as a tender plant, and as a root out of a dry ground: he hath no form nor comeliness; and when we shall see him, there is no beauty that we should desire him.

But when the other guy shows up, will it not be similar to:

II Samuel 14:25 But in all Israel there was none to be so much praised as Absalom for his beauty: from the sole of his foot even to the crown of his head there was no blemish in him.

When the beast shows up, will people be so taken by him, similar to people screaming & swooning when seeing the Beatles live? Will beholding the beast take someone's breath away? Will hearing him speak be almost hypnotic?

Regarding Jesus:

Hebrews 4:15 For we have not an high priest which cannot be touched with the feeling of our infirmities; but was in all points tempted like as we are, yet without sin.

But the other guy:

II Thessalonians 2:3 Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition;

Jesus without sin, but the beast is that man of sin.

Everything sinful in the fallen nature of man will instantly identify with that man. 

He'll be everything that man's sinful flesh desires to be.