This is about reparations and thats the reason why the countries responsible abstained or voted against it.

Obviously most countries today condemn the modern slave trade. Doesn't mean they'll do anything about it but they do condemn it

Here's a press release from the resolution. The "Transatlantic Slave Trade" as a proper noun refers to the historical kidnapping and taking of Africans to the New World to be enslaved.

The resolution emphasised “the trafficking of enslaved Africans and racialised chattel enslavement of Africans as the gravest crime against humanity by reason of the definitive break in world history, scale, duration, systemic nature, brutality and enduring consequences that continue to structure the lives of all people through racialized regimes of labour, property and capital.”

It doesn't enforce reparations, but:

It affirmed the importance of addressing historical wrongs affecting Africans and people of the diaspora in a manner that promotes justice, human rights, dignity and healing, while emphasising that claims for reparations represent a concrete step towards remedy.

The US objected:

Furthermore [per the ambassador], the US “does not recognise a legal right to reparations for historical wrongs that were not illegal under international law at the time they occurred.”

I'll note for thoroughness' sake that it not having been illegal under international law is basically true but 1000% beside the point (obviously). The US Supreme Court actually heard cases in the early 1800s about how slavery was treated under e.g. the Law of Nations, but evidence was scant that it was prohibited, and the court more or less (oversimplifying) had to make shit up. The important point is that you can't say "Oh, well the perpetrarors collectively didn't prohibit it, so there are no grounds for reparations." It's obviously ridiculous.

And Canada, and Japan, and Australia....

France still holds Haitians financially responsible for...refusing to be slaves over 200 years ago. Haiti has such a rough time now because the US and EU continue to punish the country for representing the only successful slave revolt.

I still only see two real countries.

Idk, the far right has taken over Italy, Germany and probably France, soon. The people in these countries, whilst not as awful as Americans, are/can still be very uncaring and sociopathically self-centered on average (I'm a well-travelled frog, not just an "external hater").

I read 3 voted against so i instantly zoomed on Israel just to make sure.

Jewish Holy Scriptures are not against slavery at all. They go in large detail about how to treat the slaves.

Leviticus 25:44-46

“‘Your male and female slaves are to come from the nations around you; from them you may buy slaves. You may also buy some of the temporary residents living among you and members of their clans born in your country, and they will become your property. You can bequeath them to your children as inherited property and can make them slaves for life, but you must not rule over your fellow Israelites ruthlessly.

https://www.biblegateway.com/passage/?search=Leviticus+25%3A44-46&version=NIV

And yes to slavery for millions of people imprisoned because cops lied about what they did.