https://db-engines.com/en/ranking_definition
Lots of historical mentions. Even the MariaDB website mentions it. Lots of people say "MySQL" generically to include its forks.
The percona distribution is very good!
But yes, it is very bad.
New projects get MySQL too because we know it and it works.
You are right if you look at the current state of how MariaDB and MySQL diverged. But if you migrated right at the time of the split or close to, they were not different in a meaningful way.
> unless it is absolutely necessary
Staying free of Oracle is often deemed absolutely necessary.
I know you mentioned that all you know about databases is following instructions, but maybe the folks at EDB or Percona can give you a hand.
Postgres will be around for a long time, and I think it's pretty obvious that MySQL won't.
Have you tried it doing it yourself?
Postgres is work. Mysql is not. I say this having used mysql, postgres, oracle, sybase, mssql, ingres, rdb, dbase, and other random data stores in production.