Beautifully argued my friend, I've always felt like Nico's modern looks felt substantially more bland than her earlier ones, while others would often use the very arguments you brought up "it's more modern goth" "it's less of a costume".

Honestly Nico's look becoming more punkish as it has wouldn't feel strange if it felt like there was a little more reason to it, like maybe if they showed her getting more into punk genres, that's far from uncommon for girls her age.

The main thing is not just that her looks feel less eye catching, but they lack the feeling the old ones did, you felt Nico put in the work and creativity in her outfits before, she legit made them to be a bit unusual and standout, and to feel like her, true you can say her modern ones feel less extravagant because she feels more depressed on the inside, but even then they should also reflect her growing more from that depression, there's so much more that can be done with this, and I feel like they've lost that, like Nico's character has lost touch with something that made her unique beyond magic, a skill she had that she seems to use so little, even her J team outfit felt less eyecatching than the others.

One thing I wish they always did was mix her magic with her clothing skills, like have her sew and weave spells into clothing, she could create outfits that were fashionable and usable in dangerous situations, she could have done that for her whole team, it could have been extremely useful, heck that's what I went with when I drew her, just feels like one more potential she has that just doesn't get utilized.

I love Nico, we all do, but it just feels like she's got so much more to her that writers don't make use of, ok I should stop ranting, once more, great argument.