I don’t think Mary Sue or Gary Stu characters are intrinsically bad. Provided that the work is honest about it.

I prefer characters who have realistic strengths and weaknesses, and who face credible tests in the plot, which they aren’t guaranteed to pass. I like characters who fail from time to time.

I do sometimes want some escapism and such, so I’m glad Mary Sue and Gary Stu types still exist.

The Culture would be a grand place indeed

Same with me and the Game of Thrones universe