Formal training doesn't make you good relative to the potential though. There's two ways of measuring good: relative to what's common, relative to the known best, and relative to the potential best. Potential best is difficult to determine as it tends to be well above what people imagine.This is why serious martial artists have a good, in-person, instructor, and so don't have to piece together from scratch. It is not possible for someone without considerable formal training to correct themselves. You don't know what you don't know, and we tend to gloss over bad habits that creep in over the years. This is true even for experienced black belts. That is the value of an instructor that can provide feedback.
I don't play hoops, but I do karate. I've kept it up since 1966, off and on, and consider myself more formidable now than when I was a 20 yr. old black belt. My karate training, with some weight training, has allowed me to "keep dunking." I could not have reached the level I'm at from anything youtube has to offer. I've learned from the best so have no need for the inferior route.
"has allowed me to "keep dunking" "
Haha this is what I'm talking about man. You have no sense of the principles of athleticism. There are basic ways of measuring human performance and you and many people here ignore them in favor of your EGO.
PURE EGO.
since you can't think about things rationally but only through ego let's go with this:
Do the 7 mobility checks and tell me how you do. When dumbbells are called for, tell me how much weight you use. For the hand to toe weighted stretch tell me how deep you can go as well. Stand on a box or something. Can you reach 1" depth? 3"?
I bet you that Day 1 when I did these exercises myself I did better than you. Hands down. You aren't athletic.
I bet I could probably powerlift more than you too. How much neck training and jaw training do you do? What kind of max effort isometrics do you do? Do you do jumps, sprints, anything like that? Clap push ups? Throwing? Pull ups?