Firstly, there is no proven evidence that point to an old earth.
Re: How could an all-good God let an imperfect universe evolve, wouldn't that mean that He's either not all-good or not all-powerful, as some Atheists say?
You must know the answer - he didn’t and wouldn’t because all of God’s work is good. What does it matter what atheists say, when they don’t even know God. That puts what they say immediately to be doubted.
Re: the perfect creation that Scripture tells us about in Genesis would've been totally different from the ecosystems and natural processes we see today,
It is not a different creation, but the ecosystems and natural processes we see today, are a direct result of the effects of man’s sin.
Correct Nadir,
‘“You read statements in books that such or such a society or archaeological site is 20,000 years old,” he commented, “but we learn rather abruptly that these numbers, these ancient ages, are not known accurately; in fact, it is about the first dynasty of Egypt that the first historical date of any real certainty has been established.”’ --- A. J. White, Radio-Carbon Dating, Cardiff, Wales, 1955, p.10.
As for Big Bang theistic-evolutionists, well read this.
‘302. Creation has its own goodness and proper perfection, but it did not spring forth complete from the hands of the Creator. The universe was created “in a state of journeying” (in statu viae) toward an ultimate perfection yet to be attained, to which God has destined it. We call “divine providence” the dispositions by which God guides his creation toward this perfection:’ ---Pope John Paul II’s Catechism of the Catholic Church (1992).
Such is how Catholic hermeneutics and theology was twisted to accommodate Big Bang theistic-evolutionism as the Jesuit Fr Teilhard de Chardin advocated. Creation did not begin ‘in a state of journeying,’ as the new Catechism of the Catholic Church says above, but ‘finished’ and ‘good’ as Genesis reveals, in a state of relative perfection, ‘in its whole substance’ as the dogma of Vatican I ruled. ‘Substance,’ we know from classic philosophy, means ‘what something is’ and not what something can become or is becoming. After Adam’s fall, St Paul teaches creation lost its perfection and entered a ‘state of journeying’ yes, but towards imperfection and decay, not perfection as the ‘new’ catechism asserts. ‘We know that all creation groans and travails in pain until now,’ wrote St Paul, until the Lord delivers it from its slavery (Romans 8:21-23).
‘Because the creature also itself shall be delivered from the servitude of corruption, into the liberty of the glory of the children of God. For we know that every creature groaneth and travaileth in pain, even till now. And not only it, but ourselves also, who have the first fruits of the Spirit, even we ourselves groan within ourselves, waiting for the adoption of the sons of God, the redemption of our body.’ (8:21-23)
In the end of time, St Paul tells us, God will also restore the perfect beautiful incorruptible Earth and Sky He created immediately in its whole substance at the beginning of time. But according to the new Big Bang creation theology there was no such incorruptible created ‘creature’ to be delivered back to its original perfection. Again, we ask, when were Catholics taught this future revelation of a reastored creation in recent times?