There's a real problem with everything looking the same though. For a consumer product, you lose brand recognition. For a B2B product, you can confuse your users because Tool A and Tool B look exactly the same. You have to look hard at the name, kind of like prescription pill bottles.

There is little reason to invent a completely new design system if your goal is to encourage brand recognition and prevent an operator from confusing tools.

Apple/SwiftUI has accentColor for example where you can inject a brand colour. This is subtle but effective for UI differentiation - colour is a design primitive that evokes subconscious pattern recognition and can be more effective than a complicated design framework that forces a larger context switch in the user's mind.