It bears repeating and reflecting on:
For each day, five items of knowledge are required of everyone, with no appearance of boasting, who would be leader. The day of the solar month, the age of the moon, the state of the sea tide, without error, the day of the week, the calendar of the feasts of the deities.
To learn all this is a phenomenal feat of memory, worthy of huge respect. (I have enough trouble remembering my own children's names). But - just consider - if this is just learning about past events, it is a respectable ability, but it is not a powerful ability. To be a worthy leader, you have to be able to anticipate the coming events. How can you do that for so many days and years into the future? There has to be a underlying model, and that has to be a mathematical model.
I can glibly say that Easter is on the first Sunday after the first full moon after the Vernal Equinox. What a clever boy. I've learnt the baseline rule. Trouble is, I've no idea how to apply it or predict it. For that, you need a model of the astronomical cycles. To have that from observation, and then internalise it into memory as an oral tradition is a phenomenally powerful achievement.
It also seems to me that the Druid leadership was therefore a meritocracy, where the leader was the one who retained and recalled the most & best knowledge. If you can demonstrate that, no boasting is required.