I will speak of my own experience.
A few core ideas such as the four noble truths, the eightfold path, mindfulness of breathing, and the importance of sila (as well as samadhi and panna) have stuck around.
When I was younger, I had a lot of suffering, and was drawn to Buddhism as a means to understand why I was suffering. The basic template of the four noble truths became ingrained in my mind but I lacked the depth of comprehending those four noble truths in full.
I knew that I was experiencing suffering and I didnt like it. This was enough for the myself to become receptive to the 4NT.
A lot of the texts and words I would read appeared as goobley-donk as I lacked the depth to fathom them in full. I had a general idea, but that was all. Back then, I wouldn’t have been able to cognise of what nirodha (cessation) was, but as I have aged, I have recognised the phenomenon the term nirodha describes and have joined together the word with the phenomena itself.
As I have aged, my suffering has lessened, and I have cultivated depth - the same words and texts I used to read now are full of a richness of meaning. The template of the four noble truths is now less of a pencil outline styled sketch and has become more of an oil painting, with lots of detail.
My exposure to dhamma in my early days planted a seed which began to slowly germinate. Naturally, I would keep my attention and read about the dhamma when I had the time, and slowly that would ripen my understanding of dhamma - by matching what has been written about with my own direct experience.
I discovered that the rising of insight comes on a ‘need to know basis’ and what drives the insight is urgency born of that need to know. Insight comes gradually, more in a step by step fashion than a leap frog fashion.
Just by asking this question it shows that a seed was planted in you, which too, is gradually ripening. If it is of any solace, I can only suggest to keep doing what you are doing.
We may have a raspberry bush in the garden. We can provide good conditions, good fertiliser, enough water, check the acidity of the soil, but the raspberry bush is only going to blossom in its own time. There are things that we can do to support the fruiting of the raspberry, but still, the fruit only comes when the conditions are right. We cannot throw fertiliser down and expect the raspberry bush to fruit tomorrow, but at least we can provide conditions that assist in the development of the fruit.