Every single one of them I've spoken to about it says that their work is roughly 90% learned on the job. To me this makes the certifications and degrees they earned 90% worthless
This is not sound logic. Those certifications and degrees are the baseline, foundational knowledge that make it possible for the job-specific knowledge to be learned.
To use a simple analogy, you can't do calculus if you don't know arithmetic first. But in a calculus class, you learn 'on the job' all-new stuff. That doesn't mean the 'certification' of knowing arithmetic is worthless--without knowing arithmetic, it would be impossible for you to learn or do any calculus.
We need an overhaul in the way we think about qualifications for jobs.
This is a self-solving problem. If an employer puts too many or the wrong prerequisites 'in front' of a job that doesn't actually need them, they will deprive themselves of X% of actually-qualified talent and the business will be worse off, versus employers who place only the appropriate (which in some cases, can easily be 'none') prerequisite(s) that are actually required for the work.