It's absolutely true that the original source isn't automatically better. For example, Marvel Studios has had much success with their costumes emulating what was in current modern comics, but not the "classic" versions.
Iron Man was inspired by the Adi Granov version, not the 60s version. There's no way you could do the exact 60s version in live action and make it look good or believable.
Same with Thor. To take the original Jack Kirby look and transfer it to live action directly just wouldn't work, without significant alteration or embellishment.
Not that those aren't great classic designs. They'd just look silly with exact translations.
Blade's movie look was necessary because his comic look would have been laughable.
Spider-Man, on the other hand, is a great classic design that DOES translate well pretty much directly from page to costume.
And so to is Batman's classic black and grey look. It's simple, striking and elegant and the new suit proves it "works" in live action. And that's why the people who always wanted them to go for that look wanted it - because the believed it would work, and were sick of the Batman movie makers not bothering to try.
So yeah, blindly wanting it to be faithful to the source purely for faithfulness' sake isn't automatically a good idea, but with some characters, their classic design certainly allows it to be successfully done.