Science Fiction is about the impact of certain technologies (science) on human society. If your story is focused on characters or plot that doesn't revolve around that, it's not science fiction, it's a fiction set in the future.
Take Anne MacCaffrey's Crystal Singer series of books. FTL travel and communication is dependent upon resonating crystals from this one single planet, but it's just a MacGuffin to give the main character an unusual job. At it's heart, it's a romance fantasy set in the future.
Now consider the webcomic series Shlock Mercenary, which is ostensibly a farce about a merc company in the future, but one that examines the implication of FTL teleportation (and how it affects war), digital consciousness transfer, Artificial Intelligence, Antimatter power supply that can make Transuranic superheavy elements but also needs those same elements to build, deep history and a cycle of extinctions of technological civilizations. It's a pretty good science fiction!
Now, none of this means you cannot (or should not) strive for a logical and consistent background of scientific developments in your setting, but none of it is necessary to writing anything about the future - some of the most famous examples of 'future' fiction like Star Trek constantly ignore the implications of technology but still manage to spin a good yarn.
Automatically Appended Next Post:
Mad Doc Grotsnik wrote:When setting things in the comparatively near future, you may need to answer a lot of ‘whys?’.
Indeed. Fusion power and automation should produce a post-scarcity society on Earth - why not? Confirmation of (potentially long-standing) alien civilizations should promote the unity of Terran governments - why not? FTL should be weaponized - why not?
BTW, I think crossing the galaxy in a couple months is a bad decision, it makes the galaxy seem small (Star Wars makes this mistake, but it's Space Opera). There are something like a million stars within 400 light years of our own system.