such a strawman again... You don't want to be writing explicit platform specific SIMD most of the time. You just want to write a dumb function that doesn't do any non-obvious calls, doesn't cause thread contention, doesn't hide complexity, isn't going to be a nightmare to change later, no surprises.

I am talking about self-inflicted complexity that is entirely within the C(++) machine model. Avoid that complexity and you're pretty good already. Only drop down to concrete hardware arch level where it makes sense. But largely, the C machine model is still very much suited as a model for actual hardware. Writing straightforward obvious code allows you to stay in control of memory layout and the data transformation paths. It easily gets you within <<2x of what you could achieve with hand coded assembler for the >90% of the code that are pretty boring and straightforward. And obviously you couldn't get the work done in time when coding everything in assembler.

So abstractions are desired then?

I have seen plenty of self inflicted complexity in C, starting in the golden age of Yourdon Structured Method, and all those libraries that replicate C++ basic features with preprocessor macros.