Hmm, I still cant help but have the thought that it need not be so complicated. In Waharaka Thero’s How to attain Nibbana as a lay Buddhist (First Discourse), kindly translated by Janith Boniface Fernando. Thero did not explain the more complex mechanisms of how one’s gati influences rebirth, distorted sañña etc. He only uses simple logical arguments. He says the dhamma is supposed to be simple. I have quoted excerpts from the english transcript by Janith Boniface Fernando to get an idea the type of arguments:
(21.26) To find what Dhamma actually grants Nirvana, one has to get the phrase “yada nichchan – tan dukkhan; yan dukkhan – tadanaththa” clarrified. Only that much is required. In those days the disciples, having listened to this much, weren’t listening to Dhamma for hours, for years. May be one or two hours. No previous practice of listening to Dhamma even. The folks that came to the Lord Buddha to listen to what he had to say, did not even know what Buddhism is. The one who sat down to listen, by the time he got up after listening to a few phrases of Dhamma, had already become a stream enterer. So, it is very much clear now, the amount of Dhamma we should listen to grasp the concept of Nirvana, to visualsie what is Nirvana, is not so much.
He explains above why it should be simple
(38.00) “Icca” means the will or expectation, “Anicca” means not in accordance to the will. This is the cause. If something is not agreeable to the expectation, then it causes suffering. Now let’s have our thinking hats on. We don’t expect to have suffering, do we like that? No. Will it stop, just because we want the suffering to end. We don’t like suffering, but itbefalls. We don’t want something that we like to fall into disrepair. But can we avoid that from happening? It goes onto disrepair, so is this in accordance with our will or expectation? There, the Anicca means, not in accordance with our liking, it will not satisfy our expectation, unsatisfactory. Now we are feeling a pleasure, and it is going to pass. Do we like that, no. Will it stop from going to pass? Nope. It slips away. If there is something called pleasure, something called suffering, both are not in line with our liking, our expectation. Both will not satisfy us. If there is something called pleasure, something called suffering, both are not in line with our liking, our expectation. Both will not satisfy us. This is anicca, not to my liking.
As you can see, only “mundane” explanations of anicca, just logic and no metaphysical phenomenon.
(42.51) When you see the Dhamma, you see the truth, you see the Buddha. That is enlightenment. The enlightenment lies here, not in some highfalutin jargon. Thus, we have to see, that we cannot keep anything to our liking. We have to understand only this much. What is so difficult about it. We did not see this much in our way too long, samsaric journey. We didn’t have divine vision or some psychic power to see that. We were unable to see our previous births.
And he says that only this much is needed to be understood.
He also described why we were unable to understand this simple logic – we could not see our previous births. Even though some yogis could, they believe that the high realms could provide refuge, which the Buddha also saw that there will be death. So perhaps this is the “previously unheard” teaching, and it need not go as far to distorted sañña/ rebirth dependent on gati for one to reach Nibbana.
Of course, learning the deeper concepts are still helpful too.