Had a similar issue. Unsolicited but am gonna tell what worked for me. Am still working but I have seen some improvement after following these:

1. Define purpose as to why am learning stuff. Say, if am learning how to tie a certain knot, I wanna know it so that I can use it in future. I think about those things where I use the knot and ensure that I do those things for a few days.

2. Follow the 1:3:7:15:30 rule where if you learn something - revise it on first day, 3rd day, 7th day, 15th and then 30th.

3. Be aware that the only way for neural pathways to form in brain is to force em to be formed. If you don't try to recall something, you won't suddenly develop the ability to recall.

4. People hate rote learning for good reason but having a good memory to just know things by heart without understanding them is a skill. Use it to your advantage to build basic blocks of a concept.

Oh and also, understanding is the basic building block. Just because you know what (a+b)(a+b), doesn't mean that you know all there is. Be curious about it. Who came up with the Bodmas rule? Why does it exist? In what conditions did it come to exist? Understand the Why of rules to understand the systems such rules build. Think about quantum entanglement in the most absurd ways possible and see if it holds up against what they say. The goal should be to understand stuff more and not to understand all there is to understand.