I think that you have answered the question you thought you heard, not the one that was posed.
I said that the factory offers up a technical division of labour that is rationally planned. As per Engels: 'In the midst of the old division of labor, grown up spontaneously and upon no definite plan, which had governed the whole of society, now arose division of labor upon a definite plan, as organized in the factory; side by side with individual production appeared social production.' http://www.marxists.org/archive/marx/works/1880/soc-utop/ch03.htm
You quote Marx to the effect that the division of labour must stunt human development - and so it must. But since the desire to free men from the constraints of nature imposed necessity is not the same thing as the fact, there will be a division of labour under socialism - until such time that mechanisation frees us entirely from the need to work.
To try to organise a society in which there was no division of labour - until that science fiction future of total automation arrives, that is - would be to sentence the greater part of the human race to death by starvation.