Most people writing job ads spend far too little mental effort to figure out how to write a job ad: they don't read 100s of existing job ads, they don't read a book or blog posts, they don't reflect on what they're trying to achieve at that stage of the process etc.

Instead, they copy and paste phrases from existing job descriptions (internal and external). The more specific the phrase, the more likely it's not relevant to the new job, so the less likely it gets copied.

So what does the job ad contain? The most abstract and meaningless phrases collected from a bunch of existing job descriptions.

Rinse and repeat, and you get to the situation we have today.