If you want to make progress, I suggest finding a piece of content 15-30 minutes long, and listening and repeating everyday for a year. Once you have memorized the content word-for-word, then you will be able to stop hearing meaning, and actually hear the sounds.
You could also spend time with a book which explains differences like the 'th' difference in 'thin' and 'then'. I assure you that book will not help you. Many native english speakers don't distinguish between 'pin' and 'pen' but no one confuses 'thin' and 'then'. Trying to learn a bunch of rules will not work. You have to learn to hear the difference, and the only way to learn to hear the difference is to listen to the same thing over and over.
I have an actor friend, who is well-respected professionally. I once discussed how he approaches the new play that he is working on. He said that at first he just rote-learns the play, so that he can keep all of it in his head.Only after that he starts to analyze and think about the role, deeper themes and emotional flows in the play.
I also used a somewhat similar tactic to get better at public presentations. I studied and watched two presentations over and over, making notes about structure, pausing between words, content of the slides, etc. It really helped and I managed to create a presentation that people liked a lot and I was asked to give presentations afterwards in several events.
I have succeeded with the academic approach, I can pronounce English sounds without an accent when I try and with a very slight accent when I don't try (most people can't hear minor mistakes when I speak)
I can tell you the difference between apical and laminal consonants and actually pronounce it. There is not just one way to learn. But I doubt most people can replicate my success without putting in as much time into it as I have. You have to be genuinely interested in linguistics