I feel like even though I have passed the majority of the exams and some of them with a bright result, I don't remember everything about them anymore.
Well, let me tell you, you aren't alone in that boat! And that's basically a very common thing to happen and this will even progress with time, since your brain prioritizes and knows that the exams are passed and the knowledge is no longer required. And on the other hand it must be clearly said, that the sheer volume of all the different ATP subjects is well beyond the storage capacity of the human brain and at the most it's only possible to store the essential information over a short period of time.
In my opinion, the EASA ATP exams are made ridiculously difficult on purpose and it's not about testing any knowledge, since the material is far too extensive, it's more about creating an obstacle which to pass is on the fringe feasibility (for whatever purpose) and probably also a competition/fight between the systems EASA and FAA, trying to "prove/show" our system is better, we are smarter, what ever!
Instead of producing knowledgeable pilots this system rather promotes the "jack of all trades, but master of none" kind a pilot. That's a frequent complain which can be heard from airline training captains, the poor knowledge of prospective junior FOs during screening sessions. In my opinion it's a shining example of a failed concept, which needs too be revised urgently in association with real world aviation experts, like instructors, examiners and airline training captains.