The difficult part isn't knowing which symbol is which. The problem with learning the tree, or rote memorization, is that you'll learn it as a translation table. This will slow you down to well below conversational speed. You'll "know" morse, but in practice you won't be able to use it. I think that's what you were implying with "sort of worked"?

(To be clear, I'm not saying that you can't learn morse code at all that way, and definitely not suggesting that you are or aren't fluent in it.)

For a really great modern approach, see https://experiments.withgoogle.com/collection/morse (no hardware needed, just a smartphone).

In general the recommendation is not to learn that dit, dah, dah, dit means letter "P" (and you already know what sound P has), but directly learn that the sound "ditdahdahdit" corresponds to the sound of "P". And thus cut out the middle step.

There are a few more things to actually using morse:

* Clean timing

* Keying (straight keys aren't used anymore. sideswipes / dual lever are somewhat intuitive. iambic keying is not, but it's so much less exhausting.)

* Head copy (the challenge is understanding entire words/phrases, without paper, and/or buffering it in your head because writing down char by char is too slow)

* Dealing with noise (incl other morse conversations)

(This is coming from a ham radio perspective, so maybe a bit different than flying school. I'm really curious now - did you actually expect to use it back then, or was this a case of mostly learning for the test? If yes, in what situation and how? ie, would you actually use a morse key? In the airplane? Or was it more about something like recorded emergency messages or similar?)