I'm kind of in the same boat where my desire to play certain pieces exceeds my skill level.
For those of us who don't have a teacher it can be very difficult to learn a challenging piece because we don't get feedback on how to do better. Whereas with a teacher you can get help to gain techniques/playing secrets to get over the hurdles where you struggle. Little things can make a big difference here, especially in pieces like Call of Silence which have multiple arpeggio runs and gigantic leaps that demand a higher skill level.
For me; I tried to learn Wolf by Andrea Dow and couldn't. Not because I can't recognize what to play, but because I can't process fast enough to get where I need to be accurately enough to play. I worked for a month on just the first jumps and couldn't get past my tremors being aggravated because of the tension from the demand for a skill level I don't possess.
I've done this on other pieces where I've watched performances and tried to copy them and failed because I'm just not good enough yet. It's not just about finger speed or nimbleness on the keyboard, it's also about concentration and mental processing ability. So, my thoughts will probably mirror your teacher's in that super huge stretch pieces don't help advance your skills. Hammering on them might actually set you back. You need to have patience and work your way up to those works by taking smaller bites at it.
Which, as we all know, is how you eat an elephant. This is no different.