Adwaita is by no mean the standard for now, they butchered it for their weird looking desktop and their obsession with LibAdwaita, even their icons theme is totally broken and no longer follow FDO icon naming specs, KDE tried many times to reach them to fix it, but they are refusing and stating their theme is considered modern and shiny with that ugly and cartoonish look 
That’s why a modification will be coming from KDE to load their correct icons and theme on GNOME desktop to make all KDE apps looking fine and not broken with that Adwaita theme/icons.