The Russian philologist Mikhail Gasparov writes somewhere about his experience with Latin and Greek: "I learnt quite early on to read Latin without a dictionary but I can read Greek only with a dictionary". So, even if a trained classicist struggles with Greek, we, pure mortals, should abandon all hopes (or set our goals accordingly).
Ι think one of the most important questions regarding the matter of Ancient Greek is that, for many people, from the start, it is all about reading the authors. Which is praiseworthy and my end as well, but I don't think we can do that by reading the authors alone. Because it was either their mother tongue, or they were for the most part rhetoricians or at least trained in rhetoric, etc, so they were not writing for us, learners. They are in the summit, we are in the base camp. And since there are not intermediate texts (because we want to read, and not actually practice the language), the way in between is a stone wall hundreds of meters high.
So only experts can climb that and many people will despair at the very sight of trying to climb that wall (How do you become an expert when there is no climbing learning options? well...). There are no steps, there is no gentle slope, only difficulties.
This finally leads to a circular argument: since we want to read, we do not care about intermediate things (they would feel
fake, an we want the real thing; and we do not care about audios; and, since we only want to read, we do not create them. Also, since we want to read, we do not write about things of our everyday life, which could help us in grasping the grammar and vocabulary. So we get stuck and think it is impossible, and again, that we should only strive to read.
But this hasn't been historically like these and we know people has been able to write and understand and speak in Greek (I am thinking about some humanists). What we lack, actually, is the mental framework which allows us to break ourselves from this and start learning the language in a far more active way. Dialogues? Fables? Audios would be ideal, in order to create the automatisms necessary and, most notably, to help us fix vocabulary and grammar constructions in a way that mere reading or analysis can't do.
In sum: I believe we confuse the ends (reading authors) with the means available (reading, but also other things like practicing actively, using the language for ordinary things which are known to us and thus, easier to grasp.
So this becomes sadly true, but it's more of our mindset, that of the difficulty of the language. The only-reading mindset prevents and has prevented people from writing intermediate textbooks (again, they would feel fake, and so on, but that is in our mind, it is not an ineluctable consequence of the language):
And lower-intermediate level is completely useless (no news to listen to, no podcasts, no easy non-fiction and secondary literature, no undemanding Krimis). So why bother? In case of Ancient Greek, there’s no 5k, 10k runs, only a marathon.
[There are news (at least written) in ancient Greek, in the AKWN (Akropolis World News), updated by a Spanish professor at Saint Andrews, I think.]
Actually now that I think about it, my climbing metaphor is just the same us your marathon metaphor. But what do we have so we can practice? only long texts (marathons). How can we start by making longer and longer runs and more difficult ones? We lack intermediate materials, (the equivalent to the 1k, 2k, 5k, 10, 20k runs, or whatever) with which we can practice in order to get to the marathon.
But do remember the New Testament - it might be slightly different, but much of it is more in the 5-10k range than marathon. Even if you aren't interested in it directly, it's a great first text. Then there's the obvious extra reading in the Italian Athenaze (with recordings from Ranieri), Reading Greek, and Lingua Graeca per se Illustrata.
Yes! I have recently come to the New Testament as a tool for this. Plus, there are recordings on Youtube, although with modern Greek pronuntiation.
I don't see Æsop's fables mentioned very often, but I believe they can be an invaluable resource. They are short (so they can be studied everyday without becoming cumbersome and long texts), they can be easily recorded, they are hundreds, so they may provide a vocabulary of a few thousand words. Also, we know many of them because of the fables from our childhood, and many are very easily to find in translation. I believe these fables are a resource we tend to neglect but could help us improve our level and make us more independent and get used to the language. I thinkg Bedwere recorded all of them, I found them pretious.