By that saying, are you really sure Yugi isn't weak? In the whole series, he depends too much on Atem so I would say the only pros here are Atem and Kaiba. Yugi Mutou isn't worth of the KOG title.
X was also a pro duelist who was even better than Aster and Jaden beat him first of all. And Jaden has beat duelists Aster has defeated (Aster lost against Sartorius, and Jaden beat Sartorius twice, and in one of the duels Sartorius actually cheated, and Jaden). As for Zane, Aster was projected to be better than him
-_-. By your logic the only Main Character who doesn't cheat is Yusaku because everybody else has cards that work differently in the Anime then they do in real life. Also I never said that Yugi using the Heart of the Cards is cheating either, I only said using Shining Draw was cheating.
Yami Yugi had the benefit of massive plot armor. His deck honestly sucked. It was mostly a mishmash with little synergy, yet he always seemed to draw the right card every time. I mean, his only losses were because of a timeout against Pegasus, Kaiba threatening 🔥, a surrender against Rebecca just to be nice, and the Seal of Orichalcos clouding his judgement.
Jaden's deck actually had real synergy and strong fusion combos, and it would easily be more solid than Yami Yugi's deck in real life. Hilariously enough, his deck at the end of the series would be worse in real life than his deck pre-Neos. Neo-Spacian fusions in comparison to classic Elemental Hero fusions.
To be fair, all of the main protagonists had extremely lucky draws. Doesn't excuse the piss poor synergy his cards had though, because nobody, not even Yuma, who is worse than Yugi, had to many problems with synergy.
Yuma lost several duels. (Kite (Twice if you count the first duel as a loss, which some people do), Shark, twice against Roku, Bron Stone, and even against a 🔥ing cleaning robot)
Yugi and Atem had more than that. I also don't count losses as skill, but rather, the way they are dueling and what their deck is, as well as the legitmacy of their duels. Yusei technically had no loses, but I put him lower than Jaden because a lot of Yusei's wins were because of 🔥 (Example: Jean not ending his turn, if he did, Yusei would have decked out and lost)
Let's be real here, the only Jaden wasn't a pro was because the series ended right as he graduated. He defeated several pros throughout the series. Chances are he would have succeeded if the series went that far.