The person who wrote it was blaming themselves fover being alone, and finally concluded their vent by saying that some days they feel as though they are just "a mistake disguised as a human being."

Here it went like this:

Finding a partner hadoesn't always have to do with the qualities we are imbued with (or the lack of them), and this leads to the great variety of human conditions whichthat the world is made up with: unpleasant people undeserving of having kids who, despite their nasty personalities, have found someone who loves them back; lovely people who'd make great parents but are single because can't find love; beautiful people on the autistic spectrum who are single and people on the autistic spectrum who are coupled; people with a body disability who are coupled and people with a body disability who are single; people with a mental health condition who are happily married and people with a mental health condition who are single; and so on and so forth.

It's nNot yYour fFault if yYou are lLonely

We usually capitalize the first letter of important words in titles.

The person who wrote it was blaming themselves over being alone, and finally concluded their venting by saying that some days they feel as though they are just "a mistake disguised as a human being."

My heart breaks for this person, too.

Here's how it went:

Finding a partner hadoesn't always have to do with the qualities we are imbued with (or the lack of them), and this leads to thea great variety of human conditions of which the world is made up with: unpleasant people undeserving of having kids who, despite their nasty personalities, have found someone who loves them back; lovely people who'd make great parents but are single because they can't find love; beautiful people on the autistic spectrum who are single and people on the autistic spectrum who are coupled; people with a bodyphysical disabilityies who are coupled and people with a bodyphysical disabilityies who are single; people with a mental health condition who are happily married and people with a mental health condition who are single; and so on and so forth.

There is no list of flaws that has kept humans from finding a partner, just as there is no list of virtues that can guarantee people that they will find love.

I love that you said this to the person.

NIt's not the most loved way by human beings, but it is one way.

The person who wrote it was blaming themselves fover being alone, and finally concluded their vent by saying that some days they feel as though they are just "a mistake disguised as a human being."

So I gave them my 2two cents.

Normally we spell out numbers less than 10.

Here is how it went:

Finding a partner hasn't always to do with the qualities we are imbued with (or the lack of them), and this leads to the great variety of human conditions which the world is made up with:we find in the world. There are unpleasant people undeserving of having kids who, despite their nasty personalities, have found someone who loves them back; lovely people who'd make great parents but are single because can't find love; beautiful people on the autistic spectrum who are single and people on the autistic spectrum who are coupled; people with a body disability who are coupled and people with a body disability who are single; people with a mental health condition who are happily married and people with a mental health condition who are single; and so on and so forth.

This was a extremely long sentence so I broke it into two parts. The second is still long but I think it makes sense to keep it together.

This is because life is a great combination of randomnes events, which is why everything is uncertain but death.

"Combination of randomness" by itself doesn't sound right to me. I think "combination of" should be followed by more than one thing, so I would expect to hear "combination of randomness and [something else].

Not the most loved way bIt is not the way human beings love most, but it is one way.

The person who wrote it was blaming themselves fover being alone, and finally concluded their vent by saying that some days they feel as though they are just "a mistake disguised as a human being."

Here's how it went:

Finding a partner hasn't always to do with the qualities we are imbued with (or the lack of them), and this leads to the great variety of human conditions whichfound in the world is made up with: unpleasant people undeserving of having kids who, despite their nasty personalities, have found someone who loves them back; lovely people who'd make great parents but are single because they can't find love; beautiful people on the autisticm spectrum who are single and people on the autisticm spectrum who are coupled; people with a bodyphysical disability who are coupled and people with a bodyphysical disability who are single; people with a mental health condition who are happily married and people with a mental health condition who are single; and so on and so forth.

"...great variety of human conditions which the world is made up of" leaves a dangling preposition (ends in "of") which many people dislike as it sounds a bit clunky.
Instead, I have suggested something that flows more naturally.

Many people like to give advice on how to find love, but they forget that there are a great many aspects at stake that are beyond our control.

The person who wrote it was blaming themselves over being alone, and finally concluded their vent by saying that some days they feel as though they are just "a mistake disguised as a human being."

no comma before 'and' because it is not an independent clause (i.e. subject not explicitly repeated)

Here's how it went:

Finding a partner hasn't always to do with the qualities we are imbued with (or the lack of them), and this leads to the great variety of human conditions whichfound in the world is made up with: unpleasant people undeserving of having kids who, despite their nasty personalities, have found someone who loves them back; lovely people who'd make great parents but are single because they can't find love; beautiful people on the autistic spectrum who are single and people on the autistic spectrum who are in a coupled; people with a body disability who are in a coupled and people with a body disability who are single; people with a mental health condition who are happily married and people with a mental health condition who are single; and so on and so forth.

Grammatically:

to the great variety of human conditions that the world is made up of. (passable but has a dangling preposition)
to the great variety of human conditions of which the world is made up. (more correct but awkward)
to the great variety of human conditions found in the world. (avoids the whole problematic construction with a rephrasing)

There is no list of flaws that has kept/keeps/ humans from finding a partner, just as there is no list of virtues that can guarantee people that they will find love.

Many people like to give advice on how to find love, but they forget that there are a great many aspects at stakeinvolved that are beyond our control.

The loneliness you have been going through is not an expression of your failing as a person,; it is not an expression of your faults.

need at least a semi-colon because final clause is independent.

Not the most loved way by human beings, but it is one way.

alt:
Not the way most human beings would prefer, but it is one way.