SIMD is often used to evaluate complex data structures in parallel. A common case is given a row with an arbitrary mix of data types and a query with an arbitrary mix of independent constraints on those data types, to evaluate all of the constraints in parallel in the same SIMD instruction(s).

The idea that SIMD is only good for parallelizing operations over arrays of the same type is empirically false and seriously understates the capabilities of good SIMD implementations. Some SQL-ish implementations work this way on row-structured data.

Most devs seriously underestimate what good SIMD is capable of.