So people have been coping and telling me that I’m just hating on Shanks because he punks admirals and that he’s not really a Gary Stue. He’s actually a really complex, tragic, hardworking, and well written character apparently.
The biggest indicator of a Gary Stue or Mary Sue (aside from never earning anything) is lacking character flaws.
I challenge all Shanks fans to give me three clearly defined character flaws. I’ll be shocked if I even see one that people agree on.
Nah. Anything that people will say, you will dismiss it because it don't fit your definition.
Specially since the premise is flawed: we don't know enough about shanks to see him either as a Gary stu or a complex character. The fact that he isn't portrayed as a coward like mihawk or is show kicking the ass of a shitter like kid don't make him a Gary stu.
What the story hinted as flaws (That you will ignore) was:
A)non-agency: shanks seem to be pretty into destiny but, unlike BB, he seems more reactive than active. He waits for others to move before himself acting up. In story this was what made him lose a friend in Buggy as we saw, as well as the chance to be pirate king since the actual actors will be the ones to get the prize- i.e: buggy.
B)Isolated: Maybe because of his CD origin but Shanks is the only Yonkou that is truly isolated. Let me explain: if you look at BM, BB, WB and even Kaido, they all seem to have ways to integrate new pirates to the fold and get hands to help ran the ship. From WB gaybar to BM join me and get a waifu and kaido "stay in the hole until you join". Shanks however don't have that. He has his crew and that's it. His "allies" are show to be part of a protectorate and are with him for protection. They are not crewmembers but a burden that he takes. The end result is what we saw on panel that the commanders take work that underlings should take and when they are unable to rookies like Barto are able to take territories and islands. This posture is a flaw since it makes the core members overworked when it should not be the case.
C) Brutality: combined with point B, above , Shanks and his crew don't sleep on the job. If you go against them they will kick your ass and not ask you to join later. We saw that with kidd that lost a arm and them his crew and life. That also explain why he have such a bad reputation for someone that seems so amicable: he needs people to avoid his territories since he don't have enough capable members to defend against attacks from different sides at the same time. Brutality and fear accomplish way more than peaceful talkings but makes easier for enemies to go after him (like BB and Kidd)
D) shady dealings: this is again speculation but Shanks sometimes acts shady. This may be just put for more theory crafting but Oda let the door open for a more dark ending with him and his past.
Now all of this are flaws that can be used against him in universe by a enemy, while proving that if someone defeats his core members his territories will fall apart and he will lack strong members to help defend them. What we can't say is that they will definitely apply since the character is still under construction with plenty of details hidden.