So I've said my opinion on this issue before and it's relevant to reiterate it. If Green Lanterns were just space-cops you would be 100% correct. However they are not space-cops. They're space NATO.
Even Space NATO would be impossibly overstretched trying to patrol half a billion galaxies (or even a small fraction of that many) with just 3600-7200 agents.
Suppose the Guardians patrol even one thousandth of the universe visible to
us. Then that "half a billion" goes down to "half a million."
Now, I get that the Green Lantern Corps only concerns itself with serial-planet-killing threats, things with, as you note, bodycounts in the billions.
But how often does an active serial-planet-killing threat emerge in any
ONE galaxy? A galaxy contains easily a hundred billion or more stars, and that's a lot of room for threats to emerge from. Suppose that even so, within any one galaxy, such threats emerge at a rate of only one a century, which I suspect is grossly optimistic.
With half a million galaxies for any one Green Lantern to patrol... In their patrol sector, 5000 of these once-in-a-century menaces will appear
every year. That is an average of something like... I don't know, twelve to fifteen menaces of the sorts Green Lanterns exist to combat, emerging
every day.
Which is, to put it mildly,
a bit much.
I actually think having the universe be so impossibly big actually helps excuse a lot of things in the greater context of the DC Universe and why the Green Lanterns don't actually fix the many, many planets that are terrible or why they regularly don't interfere with evil space empires. DC space regularly sucks and if it's small enough for Green Lanterns to fully patrol and cover everything 100% effectively then things like the number of massively abusive space empires that are fairly straight up evil (Sangtee, Psion, Citadel, Controller, Khund, Reach, Warworld, and Dominators bring us to 8 galactic superpowers that are pretty damn evil that the Green Lanterns don't touch. If we get into just races like the Kroloteans and the Durlans which are exmpt by virtue of not being superpowers then the number balloons even higher), the number of blown up or destroyed planets (there are a lot), the number of horrific world ending nightmares that lurk in space (Brainiac, Doomsday, Sun-Eaters, Ash'Ka'Phageus, Blume and more all exist and the Green Lanterns don't touch them) or Green Lanterns abusing their powers to set up dictatorships (there are at least 4 times this occurred while Hal was a Green Lantern) then they look straight up incompetent to ridiculous levels. I think keeping the universe massive actually makes a lot of the Green Lanterns policies and the Guardians super utilitarian mindset actually make a lot more sense.
I think it's entirely correct that the Green Lantern Corps needs to be stretched thin to make sense of all the other horrible things happening in space.
But there's "thin" and then there's "farcically thin."
I'm also of the opinion that life isn't exactly a common thing in the universe by any stretch of the imagination so the vast majority of planets in DC are utterly lifeless. The number of planets with sentient life is even lower than that and thus reduces things further.
Yes, but there's "vast majority" as in "99.99% of planets are uninhabited by sentient life" and then there's "vast majority" as in "one inhabited planet per galaxy."
If there was one inhabited planet per galaxy, then maybe the Corps could make at least a vague semblance of an attempt to patrol the universe with Really Fast Ring Flight. Then each Green Lantern would only be keeping track of, say,
half a billion entire planets' worth of major cosmic issues simultaneously.
That's still a lot of issues, though... and that's after assuming that 99.999999999% of stars do not harbor sentient life.
The problem here is that words like "most" or "a lot" or "the vast majority" or "very fast" just... don't adequately describe how big the entire universe, or even a small fraction of it, really is.
Oans are claiming the "known universe" there is stuff beyond what they've claimed they just don't touch it. That being said Green Lantern rings 100% have absurd flight speeds (Humans die of thirst in approximately 10 days, the center of the Milky Way Galaxy is approximately 27,000 lightyears. That means that even by the most extremely conservative standard that Green Lanterns only protect a single galaxy, that means that if a Green Lantern ring took Hal Jordan to Oa and he didn't die on the journey he had to be traveling at least 98,550 times faster than the speed of light).
Absurd travel speeds are kind of necessary or a lot of Green Lantern lore starts breaking down fast.
Yes- but even if they have literal teleportation they can only keep track of so much at once.
The bare fact that the Green Lantern Corps
can sort of keep up with the emergence rate of new cosmic threats and keep there from being
TOO many serial-planet-killing entities roaming their patrolled space puts some kind of upper bound on just how big a space they can be patrolling with only 3600-7200 entities. Even assuming effectively instantaneous intergalactic travel.