I started learning the piano in my 20s, and now have been playing it for over 10 years.

The key for me was to forego all theory learning and just have fun with it. Eventually, I got into it enough to go through all the memorization bits.

If piano sounds appealing to you, I recommend using software like Synthesia to make the first few months as easy as possible, to get excited about it.

I have the impression that many people learning instruments, and sadly also many teachers, take an approach that kills motivation. It seems to me that very few people want to become professionals, and that most just want to be able to play a few songs and have fun. For that you don't need perfect posture, or learn all the scales, sight read, etc.