The individual who has a breakthrough often feels compelled to call it a “system” and start telling others about it.
The great advice someone has is just what worked for them. It will probably work for others, especially if it repeats common advice, but it won’t work for everyone.
If I practice guitar for 6 hours a day (like John Petrucci in his teenage years) while always wearing an orange hat, I’ll get pretty damn good at the guitar in a few years. I can then spread the word to everyone that the best way to learn the guitar is to always wear an orange hat.
As with the dangers of ‘productivity porn’, ultimately what matters most is putting in the hours.
But one thing I like to stress is: You get to decide how to spend that time. Sure it is occasionally good to spend the time on "no fun" practise, especially if you feel your playing is lacking. But you don't get magically better results if you suffer while practising.
I'd argue the opposite: The person who has fun while practising will also learn and they will be inclined to put more hours in.