Thanos:
"This universe is finite.
Its resources, finite.
If life is left unchecked, life will cease to exist.
It needs correction."
Drawing on similar lines:
"Planet Earth is finite,
Its resources finite,
And life on Earth will cease to exist,
If no solution is found to either:
A) Overpopulation
or
B) Limited resources problem"
And since genocide never really works out for anyone,
Sooner or later, humanity will have to look at other planets
for resources, like energy, minerals and even basic living space.
Our Sun still has about 4 billion years left to implode,
So finding a habitable planet in another galaxy
or another star is a problem far into the future.