I am reproducing the content from the question, for clarity purpose.
Sex takes one away from the ultimate goal of Moksha. This
materialistic world is a place of suffering and pleasure, but more
biased towards suffering. From all these what I infer of is
in the ideal world would be to not have sex at all, not even for procreation.
Why bring children into the suffering. Also if humans vanish from earth, it would be a lot less suffering place.
Isn't it ideal that everyone becomes Krishna follower and give up on material desires including sex completely.
If everyone follows this, the final state will lead to extinction of human species (I am not trying to save the species here, I am neutral
to what happens to the human species)
I don't know whether these ideas emerged from the literature of ISKCON or that of OP. Hence, I am presuming that these ideas are of OP only.
Basically, humans are also animals. There is no difference between the activities of humans and other living beings, except thinking ability.
The scriptures say
आहार-निद्रा-भय-मैथुनं च समानमेतत्पशुभिर्नराणाम् । धर्मो हि तेषामधिको
विशेषो धर्मेण हीनाः पशुभिः समानाः ॥
"food, sleep, fear and mating, these acts of humans are similar to
animals'. Of them (humans), dharma (right conduct) is the only
special thing, without dharma humans are also animals."
So sexual impulse is not adharma or illegal or illicit. However, what is illegal or illicit sex is a different issue.
Even Rig Veda says gratifying sexual impulse is mandatory, to proceed further in the SPIRITUAL line.
In Rig Veda I.179 (P.100), Lopamudra teaches Sage Agasthya the importance of fulfilling sexual desires.
Lopāmudrā teaches it to her husband who was inclined to asceticism.
She says that even those ancients didn't find their end destination
who, without their worldly responsibilities, just toiled and spoke the
They had to marry, they had to speak their experience, they had to
live their life to find the meaning and to achieve the success.
Lopāmudrā says to her ascetically inclined husband that this way of
invoking hardship on her by staying away from her doesn't make Agastya
complete. He has to fulfill his life before thinking of achieving
success in spiritual journey. Passion is responsible for synthesis and
guilt is responsible for deconstruction. One who has understood the
way to deconstruct and construct achieve the right plane of existence.
Agastya, on hearing the wise words of his wife, rebuilds the kāma in
him and returns to his life, his duties.
Finally, about the last query: If everyone follows this, the final state will lead to extinction of human species.
Please don't worry about extinction of humans :-), as Sri Krishna said in BG 7.3 as follows:
मनुष्याणां सहस्रेषु कश्िचद्यतति सिद्धये।
यततामपि सिद्धानां कश्िचन्मां वेत्ति तत्त्वतः।।7.3।।
Among thousands of men, perchance, one makes effort for the determined
knowledge. Among those, having the determined knowledge-even though
they make effort-perchance one realises Me correctly.
Out of billions of humans, only a handful of few will get liberation, at any given point of time. And, it will take a longer period for remaining people getting liberation.
Finally, it is the creation of the God. That God will take care of extinction issue also.