Honestly, this sounds more like a problem of your hospitals/facilities and not the CNAs. What does your CNA orientation look like? What does their skills check off look like? At my hospital, all of the techs, even the new ones, know to report abnormal vitals. Why? The HOSPITAL makes sure they know that after they get hired. There are at least a couple days of classroom orientation for new CNAs. It can be longer on a specialty unit. The new CNA also has to shadow an experienced CNA for at least a week and do nothing without that CNA's supervision unless there is some mitigating factor like the new CNA is a nursing student and seems immediately competent on the first day, at which point they only have to shadow for three or four days. I had to shadow before starting work as a CNA and I'd been on the unit for ten weeks doing CNA tasks during my externship, so obviously this is something the hospital takes very seriously. If the CNA does not feel comfortable alone at the week mark, additional shadowing is offered until the CNA is comfortable. Any task beyond the CNA I level has to be checked off by a RN if the task is offered. There is CNA II certification available in my state, but the hospital only lets CNAs perform a few of those skills, so you are a CNA I+4 instead of a CNA II once you have been checked off on those additional skills, which include inserting foleys/intermittent caths, setting up suction, and a few other things. The check off requires that you do the skill perfectly at least three times with RN supervision, after that you are deemed competent to do it on your own.
If the CNAs are not being trained at your facility, your facility is unsafe. Period. There is no standardization of education for a CNA. It is totally a wild card what training a person who has been hired has. If your facility does not train new employees in the correct way of doing things they are providing an unsafe environment for their patients, and I would blame the facility and not the CNA. It's not a CNA's fault if they got hired with no knowledge at all. That's the fault of the HR department and the facility for not following up.