Not sure regarding over-polished. :) Never a problem IMO.
Simple/complex, dynamism level, style – yes, needs appropriate balance. But it also highly depends on target domain and audience.
There are pro tools.
There are productivity tools for normies.
There are casual apps.
There are games and procedural art.
You can unleash all your designer desires you want – just need to pick the proper target.
But if there is a lot of mis-targeting due fashion trends and/or prioritizing self (designer) over the user – then you get into such global limbo.
Or in case of macOS 26 in particular – design system was made too inflexible, with one category of casual apps in mind, ignoring semi-pro and pro categories. Fashion and ego definitely played a role here.