yeah the movies plot was kind of stupid and convoluted if you think about it. they should have gone with the comic plot.
comic thanos just wanted to get laid.
seriously.
basically he was heralded as a super jesus at his birth and proceeded to shit excellence. well he knew he would die and wanted a turbo awesome baby to succeede him. so what do? well he did the only sensible thing, go across the galaxy banging and knocking up hot alien chicks. however, all the babies were shit in his opinion. until he stumbled upon lady death, the literal incarnation of death. he was like “oh shit she could make a turbo baby for sure” but she didn’t want no barney dick. so he went to destroy have of life to give as a present to her so she’d spread her legs.
so which is more sensible some ill conceived plot to help existance or a man doing dumb shit to get laid?
I think the gems gave him the power to create whatever he wanted, like turn all humanoids into plants or whatever. I don’t think they could only kill or give life. In the end though imo, endgame was Guardians of the Galaxy Vol. 2 with more superheroes.
I’ll take a stab at a serious answer here.
Movie-Thanos wasn’t really concerned with all life, as much as he was concerned with intelligent life and overpopulation.
Outside of intelligent species (like humans), when a particular species over-populates an area, they deplete the resources and starve, they live in close conditions and suffer huge losses to crowd-diseases, and/or they attract the attention of predators, and through a series of huge, horrible deaths, the population level drops back to well-below sustainable levels. And then, since there are fewer survivors to fight over resources, population levels start to rise again! That is the “cycle of nature”: population growth, horrible deaths, population collapse, and then a return to rising population levels to do it all over again.
The thing that makes intelligent life a problem for this cycle is the repeated side-stepping of the “horrible death & population collapse*” stage.
“People are being hunted by wolves!” “Can I introduce you to my friend the long, sharp pointed stick?”
“People are starving!” “OK, but we can irrigate fields for more crops!”
“People are dying of the plague!” “Yeah, but check out this thing I made from the mold of an orange!”
So instead of populations dropping due to famine or plague or other stuff, they just keep rising. But Movie-Thanos didn’t think that was sustainable either. Eventually, overpopulation would be a problem, and the longer you put it off, the father the fall when things collapsed and the more people dying from it.
Movie-Thanos wanted people to intentionally control their population, rather than waiting for famine or plague or predation to do it. So he goes, planet-by-planet, and says “you can’t keep reproducing above sustainable numbers, or tons of you will die. Let’s whack your population down to half of what it was and keep it there with the threat of more killing, and then you tell me if your quality of life doesn’t improve after you’re all done grieving.”
Even if it did plant and animal life would repopulate a lot quicker. The farms after 1 to 2 years would be able to be right back up to full production with half the population to feed thus freeing up resources. It even mentioned in the movie a world that he had taken half the life and how now it’s a lush vibrant world just a few years later.
Well.. we will wait until another Thanos pops out from somewhere.