While it's clear that the author of the linked article isn't familiar with MySQL administration, it's worth noting that the most recent versions of MySQL finally support instant column adds: https://mysqlserverteam.com/mysql-8-0-innodb-now-supports-in...

That won't save us from needing extra tooling like pt-online-schema-change or gh-ost for other types of schema changes in high availability environments, but it's a step in the right direction.