The end of the world – the destruction of human civilization and perhaps the planet – is a terrifying and sad but-not-so-unlikely possible outcome of history. But even if it were inevitable, there are ways by which I can talk myself out of believing the death/fail of humanity is the end of everything. Life might arise on other planets. Perhaps the majority of those instances also end in apocalypse, but only one needs to survive long enough to fulfill the potential of the exploration of space and time for life to be considered a success. However, even if life arose on every planet and all life were to lead to an immortal spacefaring race of beings, there would remain what strikes me as the grimmest of eventualities: The decomposition of the order of the universe and destruction of all that the past amounts to by some basic feature of the universe.
Astrophysics provides a few such theories of eventual universal annihilation: The cold death, the big crunch, and the isolation of all particles.
In the cold death, all matter eventually settles into its lowest energy state, perhaps after being sucked into black holes and regurgitated through Hawking radiation as they evaporate.
The big crunch (which has been decreasing in popularity for a long time) posits that the energy density of the universe is great enough that gravity is able to pull all matter back on itself, with everything getting smashed together in the end.
The last possibility hinges on the existence of the “dark energy” force that is causing the expansion of the universe to accelerate. If it does exist as we theorize, it may very likely cause all the bits of matter to accelerate away from each other, with the furthest bits going first; The galaxies that the Hubble can just barely see disappear, then the closer galaxies. For a time it would be just our galaxy in the universe, then our solar system, then just the inner planets, then just the earth and the moon, then just the earth, then just us floating in space, then just our molecules, then just our atoms, and finally just their constituent particles, each locked away in their own eternal solitary universe.
So even if we were to solve the problems of today, there lies a distant hurdle that any part of the universe would have to clear in order to avoid the fate of death.