Applying a widget style to multiple widgets from a single source?

Hi, I was wondering what methods people use to share a style with widgets? I found some older posts that use a custom widget back in the 4.6 or 4.9 days and mentions plans by Epic to make styling widgets easier, but I cant find anything else. Is there no such thing as a style-sheet or similar that can be used and then applied to all children of a particular widget?

It seems quite antiquated to have to manually change all widgets if you want a different look to the default UI theme, and if I change my ideas on how I want things to look at a latter date then changing dozens of button widgets seems like a very tedious way to spend an evening.