The way a strong type system solves this SQL injection problem (despite your saying it's impossible and ignoring my having shown your wrong) is by automatically escaping arguments before binding them to parameters.

Well guess what, you don't need pre-compiled statements to benefit from this feature - all you need is the hoisting aspect of it. In other words, if SQL drivers did not offer the unsafe function exec_query that takes the whole query as a string and returns a result, and instead they only exposed a hoisted version of that function that takes a list of arguments and a placeholder query as a string...

  exec_query ["john", 12] "SELECT ... WHERE... = $1 AND ... = $2"

Then there is no SQL injection problem, as the SQL database driver would always automatically escape the arguments before binding the parameters.

So if only SQL database drivers did not offer exec_query but instead forced the user to provide the whole query string in one go with placeholders, then the driver would be able to enforce security at the proper software layer - which is not everyone's program that interacts with a database.