The future only seems bad to the people of the present because they never experienced the social, economic, political, and scientific progress that brought it about. To the people of the future, their world is better off even if it is different because it is the future they chose for themselves. Example: Transhumanism considers the future to contain such massive leaps in technology and human evolution that our species would be virtually unrecognizable in both appearance and psychology, so it only makes sense that a modern day human would be horrified at first.
The so-called "bad future" is actually perfectly normal... wait a minute, where are all of the cheesy snacks?! NOOOOOOOOOOOOOOOOOO!!!
The hero travels an hour into the future, and in his brief absence, the entire world has been conquered by an army of cyborg lawn gnomes.
The heroes travel into the future to find themselves in a city of ominous dark buildings covered in propaganda. Turns out, all the inhabitants enjoy material luxury, year round free heating and freedom. Then it turns out, the heating is provided by giant baby ovens.
The future is dominated by a single political ideology, with all others relegated to history books and powerless fringe movements - so the future is a Utopia for those of the heroes who think that this ideology is right, and a Dystopia for those of them who think that it's wrong.
Averted: The future turns out to be Post-Cyberpunk - lots of fancy new technology, but nothing dystopian.
Enforced: This is a good way for the work to go Darker and Edgier for a limited time - or even permanently, if the writers are so inclined.
Lampshaded: "I leave for mere twenty years, and they screw everything up. Great."
Discussed: "Ten bucks says the future is bollocks."
Conversed: "What did this guy expect from the future, exactly? Freedom, truth and beauty just like in his own time?"
The hero(es) could only be on even terms with the villain in their present because they had the government on their side. With all of this government's resources turned against them, they all end up killed or worse in a very short time.
However, the dystopian future has also spawned a secret resistance force that is more than willing to give the hero the help he needs to fight back. Seeing what's at stake if they lose to the villain strengthens their resolve to defeat him/her/it for good.