It has to be useful for large organizations like for example IBM who need to maintain consistency on various domains, displays and media types. But I suspect it also can stiffle innovation.
It also helps small teams build faster. A shared language around color, spacing, typography makes design/engineering collaboration way smoother, and reduces rework.
A good first step is to have your color palette in your design tool of choice consistent with the variable names used in CSS.
> But I suspect it also can stiffle innovation.
Like any system: it can both be empowering or the opposite.
It's a tough balancing act. Let's say you're Adobe, and you want Photoshop/Illustrator/InDesign to feel like a single family of products across web/iOS/iPadOS/Windows: where do you want to let feature teams innovate, and where must they adhere to the system so users can navigate seamlessly across these products and platforms?
Generally UI is built around a singular look and feel at a given point in time. Trends change, people change, ideas and features change.
You eventually end up with a rebranding and along with that some sort of UI refactoring.
This approach is incredibly valuable when building something that won't change drastically when you are changing those tokens.