Folks from the present (relatively speaking) are usually, if not always, going to see themselves as superior to their predecessors and lots of things about them. Folks today would look back at the kind of clothes Aristocrats wore back in the past (including the makeup they wore, including men) and see them as ridiculous costumes as well.
It's not Picard being deliberately insulting, it's just how a guy 300+ years from now would think of our own attire including what our soldiers wore.
Indeed, we look just as silly to them as they look to us. How many times have we referred to Trek uniforms as "pajamas"...?