Here is why the mark of the beast will be so insidious and evil: if having the mark is the only way to buy or sell, that means that one must belong to the system that the Antichrist has created in order to participate in society. In this way, one is endorsing the Antichrist by using his system.
The Antichrist is the one who will establish this monetary system. Therefore, if one buys food using the mark, one is endorsing the Antichrist’s system. This is why all those who take the mark will be cursed and have plagues befall on them as described in Revelation: because they have chosen to eat of the corrupted fruits of the Antichrist.
The Antichrist will likely make this mark seem like a very sweet deal by promising everyone a stipend of money to live on. For this reason, the mark of the beast may be introduced as a cure for a failing economy. In this way, the Antichrist will become like the husband and provider for mankind, offering his corrupt fruit for everyone to live off of.
The mark of the beast will almost certainly be a type of chip or similar technology which connects to one’s financial accounts. And this chip will almost certainly contain tracking technology to track where everyone is. This is a form of slavery, as accepting this device will mean that one belongs to the Antichrist like a slave; a slave who is tracked by his owner; a slave who bears the mark of his owner. In the original Greek that the book of Revelation was written in, the word used for “mark” can also mean a “brand”; the kind of mark which is used to brand cattle or slaves, showing that they belong to their owner.
And so by taking this mark, one is saying “I belong to the Antichrist.” This mark is a sign of ownership, like how cattle are branded and how some slaves were branded throughout history. Those who take the mark will belong to the Antichrist. This is a parallel of how the seal of God (mentioned in Revelation 7) shows that one belongs to God. The mark will be Satan’s counterfeit version of the seal of God.
At the point when the mark of the beast is put into place, the entire world will essentially be under the Antichrist’s control, and so partaking in his kingdom would mean to endorse his leadership and to endorse what he is actively doing. This is why God commands of mankind to take no part in the Babylon world system which the Antichrist will establish and control.
And I heard another voice from heaven, saying, Come out of her, my people, that ye be not partakers of her sins, and that ye receive not of her plagues. For her sins have reached unto heaven, and God hath remembered her iniquities.
Revelation 18:4-5