People hold the opinion that Gwok Jing was a lousy teacher because of the quality of his students: Gwok Fu, Gwok Seung, Dai Mo, Siu Mo ....
But what was he actually able to teach, only the skills of the Gong Nam 7 Freaks. The rest was "copyrighted" by the original owners.
E.g. Chuen Zun inner power cultivation, 18 Dragon slaying palms.
These were the martial arts that really took Gwok Jing to another level, beyond that of the 7 Freaks.
Admittedly, Peach Blossom Island martial arts should have featured heavily in their martial education and would presumably have been enough to enable this generation of students to establish themselves in Gong Wu.
What it really boils down to was that:
1) Gwok Fu was to lazy to apply herself to the physical hardship of daily practice, and just relied on the reputation of her parents.
2) Dai/Siu Mo were too caught up in chasing their si mui to practice, despite having a highly skilled opponent to kill to avenge the death of their mother.
3) Gwok Sueng is still relatively young, and flits to much from one skill to another. A bit like the young Yeung Gor.
So my conclusion, based on limited evidence, is that Gwok Jing should have chosen better material for his students!!