Why is the human doomsday plot so heavy?

Although it was a British film that I watched with a foreign teacher a long time ago, of course, the foreign teacher is a British person and has a bit of a local plot, but I still can't help writing down my own understanding of the film. (It can be said to be nonsense) I
found out that the British have also begun to make horror disaster movies in the past few years. . . . . It is undoubtedly all infected by the virus, and then the British turned into zombies in batches. . . . . Fortunately, British films are by no means a replica of American Hollywood, nor are they bad films.
But all it expresses is a theme-destruction, the fear of destruction of mankind itself. In particular, the British island country is isolated from the European continent and has a deeper sense of loneliness and rejection by the European continent
. That's why this film was made. . The protagonist woke up and walked on the empty street, looking at the Royal Prison, the floor was littered with rubbish and banknotes. That kind of bleak feeling can really make me feel the end of the world is coming. This is also my deepest point. . . .
Although the ending is still the survival of the protagonists?
What does it represent?
hope?

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