> Parameterized queries.

Also happy to be wrong, but in Postges clients, parametrized queries are usually implemented via prepared statements, which do not work with DDL on the protocol level. This means that if you want to create a role or table which name is a user input, you have a bad time. At least I wasn’t able to find a way to escape DDL parameters with rust-postgres, for example.

And because this seems to be a protocol limitation, I guess the clients that do implement it, do it in some custom way on the client side.

Just like we know how to make C safe (in theory), and many other cases in the industry.

The problem is that solutions don't exist, rather the lack of safety culture that keeps ignoring best practices unless they are imposed by regulations.