I disagree with this view, for one main reason: In a large organization, there is a lot of turnover in the engineering, product management, and design teams. There needs to be some place outside of a browser where the "product's" screens live.

I'm talking about a large web "platform" with multiple page templates and user flows, not a phone app. While we had an ever growing UI kit, it was inadequate to reflect all the screens and flows in the platform, from resource pages to sections for teachers to build lessons and track assignments (think a combination of a website and an LMS).

It took me a year to figure out all the views and page templates in the "product" because no one had made time to collate them. I spent about a month before I retired collating all the screens, at various breakpoints, so that my backfill would be able to get up to speed very quickly.

Those screens can be marked up for changes, and provide a visual way to convey existing flows to stakeholders. They also are super helpful to new developers coming on board. Product managers, designers and developers can identify inconsistencies because they have images of all the screens in one place. A UI kit is in no way sufficient for this. It would be like thinking a warehouse full of construction materials was all you need to build a house, not blueprints.