Well, we'll agree to disagree on the standard of mythology, then.
For me "Batman Begins" is a poor film, full of holes and, clearly, just wanting to get to action sequences as the 'Bruce Wayne' character was someone barely known about.
Nolan's "The Dark Knight Rises" was an ill-thought out concept, bereft of understanding 'Bane' as a character and where he fitted into the Bat universe. Simply donning a cape and talking in a raspy voice should not deserve ranking as great mythology as then you would also insert the films and tv shows of the 40s, 50s onwards into that great mythology; a period where there was a lot of ridicule of the character. I think people see the iconic costume and crime fighting as a building of the mythology (which is true), but doesn't make it great, just recognisable.
The only film that bucks the poor structure, as a spectacle, is Heath Ledger's legendary turn as 'The Joker' in "The Dark Knight" as the titular character isn't the main focus and is, largely, ignored when it comes to motive.
I have always been interested in the 'Bruce Wayne'/'The Batman' split persona and we're, finally, getting it now.
This is SOLELY my passionate opinion on what makes "great mythology" for 'The Batman' and not dismissing your view and I know I can [over]analyse in what makes a good film, rather than enjoy it for what it is. I do tend to do that these days and this is just reflective of my views back then.