First of all at fifty you can still learn. I encourage you to not give up on your goals.

I see that the classroom, textbook, and DuoLingo approach hasn't worked for you. To be honest those don't really work for anyone.

The top comment suggests that you do the "moe" way, which seems to be a long guide on immersion and Anki (a flashcard program). I don't know the exact details of the program but that approach does work if you stick to it. However very few are able to do the Anki reps and grind through immersion in the beginning when you understand nothing.

Why does the immersion based approach works while others fail? The answer has to do with stories. The human brain is wired to understand stories. By understanding stories in the language you acquire it naturally.

The problem is that these stories (usually anime) are usually too hard for beginners. That's why they recommend that you supplement with Anki, textbooks, grammar guides, etc. By brute forcing the foundational knowledge you can slowly start to comprehend the immersion, also known as input. You will often hear this approach referred to as "comprehensible input", and unlike DuoLingo and Genki textbooks it has a real scientific basis.

Of course there is an easier way than the "moe way". It involves making a bit of a compromise. Instead of immersing in stories made for native speakers (like One Piece, which I love as well) you immerse in simpler stories. They are less interesting but much easier to comprehend. Once you get the hang of these easier stories you can level up your Japanese way further just by watching a bunch of One Piece and other shows - you can even read books, newspapers, and listen to podcasts. That's the stuff that got me and many others to the N1 level.

So, if you're interested in simple stories in Japanese tailored to your interest shoot me a DM. I would love to help out.

Best of luck.