I mean its the director himself saying he was inspired by Watchmen right? You can't name drop Watchmen to someone who is familiar with it and NOT have them expect "grown ass adults", "edgy", etc. That's on him not me because, as you've said, if all your taking from it is "superheros in the open in the modern day" then there are plenty of other shows/comics that did that. Hell why not name drop say Teen Titans?
As for your later point, yeah I'm aware of those general cultural differences (to my dismay - though if all the kid shows were as well written and entertaining as say Teen Titans I'd be cool with that. But they aren't!). However its not like Japan can't tell interesting stories with adults (though you know that of course
). Hell the reason Tiger & Bunny was so entertaining (and it was very popular in Japan) is because almost all the relevant characters were grown ass adults. I'd LOVE another "Tiger & Bunny" but this new show is already starting on a "bad foot" (talking first impressions here of course, I can't comment on the quality of the show yet).