I tend to agree with your general intuition that presupposing modern understandings creates all kinds of problems understanding ancient texts, some of which is in translation. But the specific case of "apokalypsis" it is kind of the opposite.
There is quite the extensive record of first/second century apocalyptic literature, (some of it even became the NT). These preserve remarkably detailed pictures of what apocalyptic thinking looked like long before Nicea.
The main thing to say is the concept of apocalypse was much broader than today's. To your question, it did mean a revelation of relationship with god, and then it also meant an end-of-times sense, and it also was political commentary, and it was also a conspiracy theory, etc. People did not distinguish between which modern, narrower concept they meant, because they actually meant the broad concept.
There is quite the extensive record of first/second century apocalyptic literature, (some of it even became the NT). These preserve remarkably detailed pictures of what apocalyptic thinking looked like long before Nicea.
The main thing to say is the concept of apocalypse was much broader than today's. To your question, it did mean a revelation of relationship with god, and then it also meant an end-of-times sense, and it also was political commentary, and it was also a conspiracy theory, etc. People did not distinguish between which modern, narrower concept they meant, because they actually meant the broad concept.