Why do atheists consider the concept of a creator as invalid?

The second thing to note is that the fine-tuning argument (if one can call it an argument), assumes that the parameters are independent and could have taken on any value over a wide range.

But from where comes such an assumption?
There is no basis for it (except that it is necessary for the argument).
If the assumption goes away... and there is no reason why it should remain... what happens to the 'argument'?

I have seen people express astonishment that the universe is 'so finely-tuned to support life'.

Really? Are they serious?

Pearce points out that the universe is actually much better at supporting black holes.

Our universe is full of black holes - trillions and trillions of them. It really does seem as if the very purpose of the universe is to produce black holes (not life). There are more black holes than potential life-bearing planets (a lot more). A lot more material in the universe is devoted to creating black holes (a lot more). The universe is almost entirely a vacuum, in which black holes, not life, thrive. We barely struggle along, having a very difficult time surviving, in brutal competition for resources on a microscopic island of life that will be destroyed by the sun at some time (if we're not wiped out by asteroids or radiation before then).

Life has a hard time starting and is very easy to get rid of. Black holes, on the other hand, are inevitable consequences of this universe... and it's almost impossible to get rid of them. Black holes are right at home in this universe.

If you want to explain everything away by merely saying 'goddit', then you might want to ponder why we didn't get:

1. a geocentric universe, or
2. just four or five fundamental particles, or
3. a universe filled with breathable air

...any of which would have been kinda nice

@newjaninev2: I disagree and I think many other would also. It is evident, that the earth has made life possible. The earth is n fact tine tunded for life if one may use that description. As of today, there is no other place found in the universe where life is possible.

@Dreammmer: "...if one may use that description"
As I said... life is fine-tuned for the Earth

@newjaninev2: And the one who fine tuned life for the earth is the God of the bible, who also fine tuned the earth for life.

and fine-tuned the universe for black holes?

We have no need of magical entities for any of that.

We understand very well the course of life's development on Earth