Changing databases is extremely painful if there's a fair amount of data already stored there. It doesn't matter how "database agnostic" the code was originally

Changing databases is extremely painful if there's a fair amount of data already stored there. It doesn't matter how "database agnostic" the code was originally, there are too many edge cases that tend to become front cases over time that you have to adjust for your specific database. But just like with MySQL, I imagine those who can migrate to another DB would do so at the first opportunity or wait for the equivalent of MariaDB to make a "drop-in replacement" in lieu of messing with their application code.