I don't think readers are as conservative regarding genre as you make them out to be. Roger Zelazny's Chronicles of Amber is one very well known example of fantasy, with no elves, no dragons, and a rather unique approach to magic.
I believe the problem is rather with subverting the expectations you yourself have established, either within the first part of your novel, or within the first book/movie of a series. The Phantom Menace came after three other Star Wars movies - after a trend has been established, and audiences had reason to expect "more of the same". Notably, since I've mentioned Amber before, the Merlin cycle is often criticised for being too different from the Corwin cycle: same issue - expectation established, and then broken.
It follows that if you intend to have different elements in your story, you need to establish all of them early on. Ken Liu's Grace of Kings is a story of politics and war, with few magical elements, except when the gods interfere. The gods appear very early on, to observe and comment. They do nothing yet, but their presence foreshadows their future interference. Similarly, G.R.R. Martin's A Game of Thrones starts off as political intrigue. What foreshadows the future presence of more magical elements in the series is the prologue with the Others, and a few passing mentions of magic "no longer working". It's mentioned that there used to be dragons, so when in the end of the book we see dragons, it's a moment of awesome, not "where did that come from".
For your examples, if you have both two elderly farmers and something with knights and dragons, you would need to present us with both from the start: show the farmers, mention, perhaps in a conversation between them, that there are knights and dragons, and those might affect the crops. If you want both space battles and political intrigues, you can show, from the start, that your character is capable of both, or maybe you have two different characters each engaged in one of the two - introduce them both. You don't need to be specific, but you need to provide some hint to the reader of the varied elements that will be present. You don't want a major story element to come out of left field.
If you are working on a series, and have already established some expectations that you now need to subvert, that is harder. As mentioned above, Zelazny received criticism for this. Here I would recommend a balancing act - on the one hand, maintain enough familiar elements that the story doesn't feel completely different. Remember your readers expect "more of the same". On the other hand, tell the reader, in no ambiguous terms, that "more of the same" isn't going to happen.
For example, Jim Butcher's Dresden Files series started out as a series about a wizard who is also a private investigator. Every book, there was a case to solve. Then came Changes - a book the very title of which suggests change. (Major spoilers ahead)
In Changes, Dresden's apartment, office and car get completely and irrevocably destroyed, and he himself dies. After this, you know there can be no going back to the way the series worked before. And indeed, when Dresden comes back, it is as a powerful entity's hitman.
Despite the major change, the characters in the series remain the same, providing enough of an anchor so the series doesn't feel like it's an entirely different story now.
Other combinations of familiar/new are possible. For instance, a character might "pass the torch" to someone new, but the series would remain the same in its premise, in what the audience could expect to happen. Consider the transfer from Star Trek to Star Trek - the Next Generation: different characters, same premise. Again, there was enough familiar that the story didn't feel entirely unexpected, but the change to a new series and a new century let the audience expect some change.