I think we'd all be gladly sitting atop high abstractions like that if not for the fact that brands pay the bills, and brands want custom experiences. Website and app design often begins with "what does a button look like," and design tools focus not on prebuilt widgets but on paths and fills, because the last thing a brand wants is to speak with different tones in different media. Their software has to feel like their stores and advertisements in order to create a brand-consistent customer experience. Design systems are a hot topic today because what brands got with this design method is a different voice in each of their sites and apps, because they're all independently custom.