Isn’t this just labels and page properties?

Labels are flat, free-text and easy to misspell; page properties need a table on every page and can’t enforce anything. Metadata gives you typed fields — text, single- and multi-select, date, user, page link — grouped into Content Categories like “Process”, “Product” or “System”. Fields can be mandatory, values stay consistent, and the Metadata Report macro pulls them into a live, filterable overview across spaces that updates itself.