One thing I hate about guys that complain about Mary sues is that they never complain about “Gary Stus.” For example, Light Yagami was kind of a Gary Stu. He had an IQ of 215–230, he was handsome, the most popular kid in his school, and his family was upper middle class. Jace Wayland from Shadowhunters is an arrogant, brooding bad boy who’s a master martial artist, who women fawn over, and is basically the fantasy of what men and women think a cool bad boy is. Tony Stark is a multi-billionaire with multiple armored, superpowered suits that basically make him Superman, and Superman himself is basically a god.
Are these characters bad? No. I love all of them, but let’s be real here… they could be considered male Mary Sues, and these guys never bring that up.
Now, not every character or show has to be relatable. Peter Parker works because he’s an everyman; however, the opposite can also be true, and people like fantasy escapism. That’s why soap operas about wealthy people or sitcoms about financially stable families are popular, because it’s a form of escapism this goes for Mary Sues and Gary Stus too.
I’ll give you a better Gary Stu example - Superman. The guy was originally designed to be all-perfect, all-knowing, all-seeing and incredibly strong with a reinforced moral system for good. He has to always be the one saving the day, he’s got the looks and that ran for a very long time. Up until the 90s did we get ballsy writers to actually kill him off temporarily, but even then he came back shortly after renewed.
Quite frankly, I don’t like Superman that much for that reason. Sure he’s been going through different arcs in the past 30 - 40 years that challenges his mystique but I can’t care enough for him to even feel slightly in favor of him.
Batman is more of my level. Sure, he has his fair deal of plot armor, but his origin has always been that he was just a guy who has a lot of wealth and wears a bat suit while wielding lots of technology at his disposal. He can still get his ass kicked, he can still be succumbed to everything a normal human would suffer with and isn’t too afraid to admit that he’s human who would need help from more capably powerful heroes.