Not impossible, we don't know exactly what was meant by that. It could be regular corruption so bad that there was no other option left or it could be something genetic making them something other than fully human, this is still debated.
If it is the latter then it's being repeated with trans-humanism.... not to be confused with trans activism. Many suspect demonoid hybrids are either already or will soon be making a comeback.
Also... you place a great deal of value on animals when Biblically speaking they are far less valuable than humans.
We just don't have enough information to say anything conclusively though the evidence points heavily to mass genetic corruption of some sort including animals.
Actually a flood was the perfect choice. It did the cleanup while leaving evidence still observable today. On the other hand you seem to be equating death with an ultimate end. If the children could be killed in a quick way before they were corrupted and sent straight to heaven would this not cause less suffering than slowly dying because their parents were taken out of the picture in an instant? How would a handful of people take care of many thousands of toddlers?
The narrative of the Bible is one of a God who progressively removes Himself so His creation can become independent, nowhere do you see a nanny god that micro manages everything in the smallest detail.
On the other hand.... what makes you think any mortal man has the capacity to know what is best given his obvious limitations nvm his limited brainpower?
Not true, the Bible is full of it. The Judgement on Jerusalem was a collective punishment. The earth being destroyed in fire in the future will be a collective punishment. I am thinking massive solar storm.
Your first mistake is thinking it's either or when both individual judgement AND collective judgement is applied depending on the situation. Pick any story in the Bible and you will find both not just one. For example a whole kingdom is devastated, individuals are saved.
Your second mistake is thinking in materialistic terms about a spiritual universe where the physical plain is merely a lower dimension.
Just because something is not true right now does not mean it never was or never will be.