Yes it takes years to learn. But good advice and instruction can take years off the time it takes you to learn to play well. And unless you learn to do things well, no matter how much you play you'll always be limited. I know plenty of guys who play 2-3 times a week and have for many years and yet they don't get better. Their technique will always limit them.
It's great for you that apparently you never needed any help or advice. But as you said at the end of your post: it's like boxing, unique to you. Everyone is different. Some people get a lot from receiving help from others. Why do you care so much? Did you really come to the sub forum for Tennis Tips/Instruction purely to complain about people asking for... tennis tips and instruction?