Is it actually less appealing? My understanding is that DBAs consider Oracle very good, just very (very) expensive. This also lines up with my experience tuning queries against Oracle vs Postgres backends. The folk wisdom seems, to me, to be Postgres is 99% as good in the common cases and 90-95% as good in the difficult cases.
Oracle DBAs consider Oracle clearly superior. SQL Server DBAs that know all the ways to optimize SQL Servers consider SQL Server clearly superior. I don't know of any PostgreSQL DBA, just generalists that work with Postgres, so I don't know about them.
The truth is that Oracle is ridden with coherence bugs, and have a much worse performance picture out of the box than Postgres. But while improving the Postgres performance requires deep digging into the DBMS itself, Oracle has a lot you can optimize just on the SQL interface. But there are plenty of cases where Oracle just can not become as fast as out of the box Postgres, and many where it could in theory, but a bug prevents you from doing things right.
Overall, three is no definitive ordering on the speed of the "good 3" DBMS. It always depends on what you are doing.
