どころか is used to emphatically deny one statement and present a reality that is far from it – often the opposite extreme or something even more surprising. It conveys the meaning of "far from," "anything but," or "let alone."
The most common use of どころか is to strongly deny a moderate expectation and then state that the reality is drastically different – usually the opposite.
Here, the speaker rejects the first idea entirely and replaces it with something unexpected.
どころか can also mean "let alone" or "not to mention," emphasizing that even a lesser or more basic thing is not the case, so the greater thing is obviously impossible too.
In this pattern, the second clause often includes particles like も or さえ to emphasize that even the more basic thing applies.
どころか can also escalate in a positive direction, meaning "not just X, but far beyond that."