Not obvious to me. We just implemented a streaming solution using the iterator interfaces. They are just functions so reading the code its easy to understand. Adding special language support only serves to obfuscate the actual code.

Go provides generic types since v1.0 - maps, slices and channels. Go also provides generic functions and operators for working with these types - append, copy, clear, delete. This allows writing clear and efficient code.

There is close to zero practical need in user-defined generic types and generic functions. Go 1.18 opened Pandora box of unnecessary complexity of Go specification and Go type system because of generics. Users started writing overcomplicated generic code instead of writing simple code solving the given concrete task.

I do agree with his point that the implicit mutation of the loop body for an iterative will be difficult to debug.