I don't understand this criticism. First I don't think it's the case that a movie HAS to be epic, there are plenty of examples to the contrary.
Well, no, a movie doesn't have to be epic, but it should tell a story that is important to the characters. In theory, a movie should depict the most important event in its characters' lives, or at least a major, life-changing event. An episodic series is a different matter, because you typically preserve the status quo (although that's less true now than it was when TOS was made). In more modern terms, I think it was Joss Whedon who said that a TV episode is a question but a movie is an answer. That is, an episode of a TV series (the modern, more serialized kind) moves the storyline forward a bit but is setting things up for later payoff. A movie should be more about the payoff, the resolution.
So a movie can have a small, personal story, but it should be one that's important to the characters' lives, one that changes their status quo. This is where Insurrection fell short; ultimately, there was little sense of any meaningful impact on the characters' lives. The filmmakers started out with ambitious plans to do Heart of Darkness in space and maybe even force Picard to kill Data, but they ended up with a film where Picard's only arc was that his life had become too cluttered and he needed to learn to slow down and appreciate existence.
But at any rate, I didn't mean that TFF was less epic, just that it actually took Star Trek back to its roots, with exploring the unknown rather than dealing with politics, a battle with an old foe, rebelling against Starfleet etc.
Well, to an extent. Technically, their mission in that film was to free a group of hostages, and the exploration was done under coercion by the antagonist. So it's not entirely a return to Trek's roots.