Design systems have been a thing for years, it's mostly the terminology getting more traction now. Frameworks emerged for a lot of reasons but a key one was people wanted repeatable ways to produce their designs, particularly at scale.
To look at it another way - if you're using a framework without your own specific design, you're basically using someone else's design system. That's fine for any project or business where design is not a key business advantage (eg. maybe it doesn't matter if your website looks like everyone else's because your business is selling a product, not the UI itself). Or a personal project that just needs a UI that works - use whatever you can build quickly.
But anyway, as a literal answer - yes, at work we use a design system.