Wuji also have good foundation especially after training with Z3F in Wudang for 6 months yet he still lousy time after time also YG never fully mastered his previous skills until he meet bro condor and trained with DGQB sword art he also didn't have great teacher like H7G or ZBT (GJ) or Z3F (Wuji) but he never clumsy during fight..
I think Cheung Mo Gei underperformed against the Dao-generation monks because he was distracted by his guilt over Chow Chi Yerk and because he respected the Shaolin elders and didn't want to risk harming them. He did not yet have that level mastery where he could defeat them without harming them.
During 2nd duel against Du Monks he only fought Du E and Du Jie since Du Nan was "busy" with YX and Eagle King yet Wuji couldn't win as usual he fought stupidity he try to force them to internal energy duel rather than use his superior external skills if we remember XF easily toying with Xuannan and Xuanju in You Manor mostly due his superior external art though he only use Founder Long Fist but his mastered kungfu really beyond imagination..
As I said, he was not yet at that level of mastery where he could defeat such strong adversaries without seriously injuring them. That takes a high degree of skill that I don't think he had yet.
Cheung Mo Gei's external skills mainly rely on using Keen Kwun Dai Loi Yee to "copy" the external techniques of whomever he happens to be fighting. This only works on weaker opponents, however. His independent external skills were mostly limited to Tai Chi Fist and Tai Chi Sword...skills which he notably did not draw upon to fight the Dao-generation monks (perhaps they did not suit the occasion or these particular adversaries).
Yes. His external skills tend to be defensive in nature. He does not seem to have an external skill that is well-suited for attacking first.
I also think that he was never quite focused during the entire time at Shaolin because of Chow Chi Yerk and Chiu Mun. His mind was elsewhere, even during those intense fights.
But when he fought Xuanming Elders in Dadu (Beijing) he easily dominate them JY even said Wuji could kill He Biweng if he want to kill him and at that duel Wuji never know anything about Persian martial arts yet he still could "toying" with Xuanming Elders but when he fought Du E and Du Jie he struggling to beat them even after he learn Persian martial arts and we know Du Monks only a bit better than Xuanming Elders so if isn't JY inconsistention Wuji logically could beat Du E and Du Jie with easy..