You're right and those were relatively minor changes to Batman and Superman. Can you imagine if both had changes to the level of the upcoming turtles movie were even the core things present in every version are fair game to mess with. Fans would complain way more than the lack of underwear.
What really bites for me is the argument that they have to go in this direction to translate to screen when we're living in age were faithful comic book are killing it. All the best of the current crop of super hero movies like Iron Man and Winter Soldier have stuck close to the comics.
When I saw Batman Begins to me it was an adaption The Man Who Falls, Year One, Year Two and The Long Halloween. When I saw The Dark Knight far from a bold new take on Batman it was one I'd always wanted to see brought to life from page to screen. Obviously it translated differently but it was clear Nolan knew the mythos inside and out so most of the alterations still felt true to the concept.
The backlash actually been pretty important for this movie as it has facilitated change. Make no mistake had it not been for the meltdowns over the aliens issue we'd be getting something very much like that Blue Door script and they've prided themselves that they're made changes even while on set to appease fan concerns but I would argue that if they don't really get why fans were upset in the first place I don't think they have the correct knowledge of how to fix them The weirdest thing is TMNT shouldn't be hard to screw up. At very best it could be the equal to the best comic book movies and at worst it's just a fun romp. Obviously they've gone for the latter in their own "Michael Bay" way but they didn't have to offend so many people getting there.