If the boosters are correct about the trajectory of llm performance, these objections do not hold.

Debugging machine code is only bad because of poor tooling. Surely if vibe coding to machine code works we should be able to vibe code better debuggers. Portability is a non issue because the llm would have full semantic knowledge of the problem and would generate optimal, or at least nearly optimal, machine code for any known machine. This would be better, faster and cheaper than having the llm target an intermediate language, like c or rust. Moreover, they would have the ability to self-debug and fix their own bugs with minimal to no human intervention.

I don't think there is widespread understanding of how bloated and inefficient most real world compilers (and build systems) are, burning huge amounts of unnecessary energy to translate high level code, written by humans who have their own energy requirements, to machine code. It seems highly plausible to me that better llms could generate better machine code for less total energy expenditure (and in theory cost) than the human + compiler pair.

Of course I do not believe that any of the existing models are capable of doing this today, but I do not have enough expertise to make any claims for or against the possibility that the models can reach this level.