"People create smaller people.. Children?"

I still don't know even why people just have some bs complaints about this scene.. Like "This was an attempt of a poor joke"... seriously?

Actually it isn't even an effort of making joke. The whole dialogue was "Everyone creates the thing they dread. Men of peace create engines of war. Invaders create Avengers. People create... smaller people? Er... children! I lost the word there. Children. Designed to supplant them. To help them... end."

Ultron chuckled in that scene because he found the concept of "having children" silly and useless. He realised (remember again, he didn't know much deeper about humanity, he had only a vague idea) children are just made for serving the purpose of replacing their parents eventually. Human beings fear death but as death is inevitable and a natural process to humans, they create their own replacement (children) even though knowing someday children are going to take their places. Ultron finds this philosophy of human beings ridiculous

Now though Ultron could make his own army, upgrade himself into another body, but the AI of Ultron never gets "replaced". Even the Ultron bots were linked together through the AI of Ultron.

Calling it a "poor joke" or some other bs is just a sign of being a "casual viewer"