Even when a company like Google or Facebook uses "mysql", it's not stock Oracle MySQL -- which is what people are going to download and use when they hear that

Even when a company like Google or Facebook uses "mysql", it's not stock Oracle MySQL -- which is what people are going to download and use when they hear that MySQL is good enough because major companies use it. This is an unfortunate situation caused by most distributions still favoring stock mysql over percona, and Oracle refusing to incorporate patches even when they're plenty of evidence that people who know what they're doing want those patches. It seems like Oracle is more concerned about trying to keep mysql less well suited for major deployments, so it can upsell its flagship product. Or else their development process simply doesn't properly accommodate community assistance. Either way, as long as their resistance to community-aided development continues, mysql and oracle/mysql disparagement will continue, not because people hate Oracle, but because Oracle's management of mysql makes it less than ideal for those who simply want a good open source database. Which is the point of the OP. Anyone who is open to looking at options and who wants a good open source database should look at PostgreSQL. I doubt any of those example companies you listed even use stock Percona. Facebook for sure has extensive modifications beyond even the publicly available distributions like Percona and MariaDB.