True Dat!
I like the 500 hours method though. If you just plow through your practice and lessons, while difficult as you go but looking back at the 3 months mark or around 200+ hours you’ll be amazed at how much you have achieved. I do that “dog with a bone” approach on much of everything I do, except for guitar, 
If I’d done that I’d probably be a decent guitar player by now.
I have 20 new songs I’m learning right now for a visiting artist in March. I just sat down and put up the sheet music in front of me and just go at it. Full speed sight read did that twice today and it’s doable.
My next session, I’d break it down and slow it down and commit them to memory. 2 sets of 10, 90 mins each day til middle of February, then combine both at full speed until rehearsal, after that play them in 3 keys, It’s doable.