I’d assume it’s lampshading (CAUTION: tv tropes link). The writers and artists know that it would be weird irl to wear those uniforms but they (or someone) decided they’d make for flashy covers so the uniforms stay and the characters get to be a bit snarky about them.

Edit: added tv tropes rabbit hole warning, I’m so sorry if anyone already fell into one, there is no excuse for my behaviour.

Lampshade Hanging - TV Tropes

Lampshade Hanging (or, more informally, "Lampshading") is the writers' trick of dealing with any element of the story that seems too dubious to take at face value, whether a very implausible plot development or a particularly blatant use of a …

TV Tropes
I don’tthink so, this isn’t a general “aren’t superhero costumes whack” thing. Jean and Banshee have other costumes that’d be just as out of place irl but they only complain about these ones
I’m not saying it’s a general thing, they’re talking specifically about the yellow-and-blue/black spandex that has been target of more or less friendly ridicule forever. You also can’t expect them to snark about everything that might seem weird, it’s not a parody.