Writing your code in assembly wouldn’t have isolated you from any of these issues; in fact it would make deploying the kinds of mitigations mentioned in the art

Writing your code in assembly wouldn’t have isolated you from any of these issues; in fact it would make deploying the kinds of mitigations mentioned in the article drastically more difficult. And even if you’re actively thinking about micro-architectural concerns, it is evident that these issues are not obvious, since it took a long time for anybody to put their finger on a concrete problem with speculative execution.