MySQL 8 has a lot of functionality that MariaDB lacks.
People like to criticize MySQL for some bad engineering decisions made decades ago. For whatever reason, often these folks have a more positive view of MariaDB, but without stopping to consider where all those original MySQL engineers went. FWIW one of the footnotes in the original article touches on this too.
Pretty much only three reasons: you want Enterprise support, you don't want to think about license terms, and you really want to help pay for Larry Ellison's personal island.
Last I checked mariaDB still misses some functiinality around JSON, and i don't know what the story is exactly about compat. With the newer X protocol and its collections.