on the other hand I wonder if all these people are replacing the ideas of Christianity and Communism for creating the perfect human without 'flaws' or imperfections in Paradise, where everyone is equal achieving a 'Nirvava' state of being.

The ideas themselves, in large part, were never wrong. Wanting a perfectly just God to punish evil and reward good wasn't wrong. Wanting to live forever wasn't wrong. What was wrong was the notion that these deities existed. That's the difference between religion and transhumanism: the latter is real. We can actually direct effort toward it, instead of just praying and waiting for things to happen.

So perhaps we needed religion back when there was no way for us to achieve our dreams of immortality etc., and so religion kept us from feeling everything is futile. But now we can rid ourselves of our religious shackles, because finally we see a way for us to realistically make things happen.