>The rarity of goldilocks life-friendly plants seems far outweighed by the astronomical number of planets that must be out there...

This math gets to be complicated even for people skilled in it. But with the assistance of Claude 3.5, using a specific estimate of one septillion total stars in the Universe, and fitting only a couple of extra (beyond the Goldilocks distance) yet basic likely required variables like Star type and axial tilt (my position is that there are very likely many more required variables), the total number of possible planets in the entire Universe is around 100 million iirc. And that's without variables for multiple Solar System bodies that may need to further align. With the closest possible planet probably being a distant 2.5 million light years away. The possibilities could rapidly reduce in probable number, if one or more extra variables were fitted. The number of extra variables that may need to be fitted is unknown. However, multiple characteristics of Earth exhibit multiple remarkable correlations with characteristics of the Sun, Moon, and possibly more. Are correlations of these types required for a Planet to form a life supporting atmosphere and surface? It's a strong possibility in my opinion.

There are a lot of planets. Though, the number of planets that could hold life may be overestimated given probable underestimation of the required confluent factors needed for life.

>I'm not sure where you are getting "vast absence of life in the Universe" from.

Really? Even "close" distances between intergalactic bodies tend to be beyond most people's ability to comprehend them. Life is absent in those spaces, and these distances comprise almost 100% of the Universe. In addition, the only known life in the entire Universe is on this planet. Everything else is speculation until proven otherwise.

>It's good to feel lucky/thankful for ones own fortunate circumstances, but merely existing isn't really one of them.

I and many more would disagree. Perception on this matter is personal, and in part a factor of intentional specific use of one's cognition to appreciate how rare and unlikely this is.

>If you are a drugged-up child soldier in Africa, who has just been forced to kill your own parents, then should you be feeling lucky to be alive?

That this is hypothetical aside, in my opinion there's nothing more true on this matter than the assertion that you'd have to ask them. Whether or not you and I approve of their existence is another matter.

Nightmarish miseries have always existed here. As has bliss. They've never been justly meted, and about as far from evenly as possible.

Still, that dichotomy and everything else that characterizes life is a part of the total human experience. We've never had one without the other, and may never unfortunately. That may be the nature of life.

Therefore the essence of the question may boil down to whether or not you and the median child soldier would rather this collective existence of unjustly partitioned joy and misery, or instead nothing but the cold vacuum of a completely lifeless Universe.

I don't think that it's rational to marginalize the specialness of the experience of this Life just because misery exists. Though, for sure many people would agree with you while many would agree with me. Both miserable and not.

Most people have been miserable at some point and most have gotten through it, extreme circumstances aside. Are most people who come through their misery happy to have remained alive to see the other side of it?

You're likely to have had ancestors that lived extremely short, violent, and miserable lives. Possibly somewhat parallel to that of the hypothetical child soldier. Yet, they or their siblings persevered to reproduce, and down the line some their relatives likely experienced lives full of relative happiness abetted by the possibly unlikely gifts of this Earth. Would it have been better for none of them to exist at all? Alternately, we might accept that Life here is a unique miracle, to our knowledge, which has a striking and inescapable dual nature.

That said, everyone looks forward to a future wherein we can eliminate such nightmarish human misery as much as possible: ideally to zero.