Ok. I'll agree with at least one other in this topic that the modes are simple enough. Not sure how 'myth' even applies. They are what they are. To me saying there is a myth implies that they somehow are not what they seem. I just don't see it. No mystery really.
Now this post sorta sums up the myth of modes idea......not quoting it for any other reason than to maybe remind those reading this great tread of a point i made earlier on.
So modes, as i said, help enhance what you already know, so the more you need to know...the more they will help and vica versa......
So if you are new to theory ideas then you will not be up on the idea why modes are considered a "myth" to bestowing those that learn them magic understanding of music.
There will be those with limited experince that focus the word myth and take it literally, and those with vast and ranging experience that will take it in the context they know it is being used.
But you have to know the context.....the more you know about this sort of discussion the more you will get the myth of modes...and vica versa.
Also someone mentioned modes and fingering patterns being distracting, or leading to just playing shapes....well music theory is not for the instrument, so do not learn on your instrument, learn using pen and paper.
Write down what to learn, work on it on the paper, then transfer it to the instrument...and back to the paper a few times till you get it.
If this seems to hard then get Trombone music books, and books about how theory applies to Trombone, as a Tromebone uses slide positions, not fingerings, then learning about modes from a Trombone book will cure this problem....and of course the more you know.......and visa versa on this point.