Yes, I have seen the similar questions. But they do not satisfyingly answer my own since my question is slightly different. Let me explain:

I was reading up on Emptiness, Samsara and so on and found out that there is no individual soul or energy that reincarnates. Rather, it is like a candle lighting another whereby the wax of the new candle is different and has nothing in common with the previous candle.
And I see that this image does not contradict (if there is no soul how can there be rebirth?) the theme of rebirth when looked at it this way.
But I was wondering about one thing:

If there is no individual, eternal essence (like the Atman in Hinduism) that is liberated wouldn't that mean that life would go extinct at a certain point? I mean if I understand the Buddha correctly we all return to the one "collective", true essence that he called the unborn, unchanging etc...
Doesn't that mean that at the point where all beings were liberated life would cease to exist?

So my question is why did he teach to free oneself from rebirth when looked at it from the perspective I tried to describe?
Come to think of it the Buddha seemingly never answered questions of the origins or the fundamental workings of the universe. For example I know he was once asked what would happen to a fully enlightened Buddha after death.
To my knowledge he would answer questions like this saying that it was meaningless to ask such things.

Did the Buddha know something about the non-self or the universe that he purposefully never taught? Is the goal of a sentient being to join the "one soul/ground of being" that is the unborn? But why? Is it bliss to cease to exist and join a "homogenous mass of energy"?

Why is it important to sever the karmic cycle if it is obvious that this is the way in which the universe manifests itself? In my opinion the universe manifesting as this myriad life forms is a joyous loving act and the whole point of the cosmic energy. I'm confused since I read that part about the Buddha's teachings...