I found this article just recently that explained the results of some independent research into the knowledge of accounting graduates.
The research indicated that only 51% of tested accounting graduates had a "strong intuitive grasp" of double entry bookkeeping.
Given that the understanding of how debits and credits work, and how to structure and process a journal are fundamental to basic bookkeeping, such understanding is crucial to providing a good accounting service.
If you engage the services of an accounting firm, it's a bit more tricky. Many of the large firms have a graduate programme where they train up graduates to full qualification. It is likely that these juniors will be doing the bulk of your transactional processing, which is then overseen by a senior. You need to trust that the senior picks up on any knowledge gaps of the juniors.
With smaller firms, it may be possible to find out exactly who will be doing your accounts. Even then, you'll need to rely on the senior to ensure that the graduate does their work well.
If you are concerned about the quality of knowledge that your external bookkeeper or accountant has, just ask them. If you don't get a satisfactory answer, think about your options to change them. Your business could be at risk, and that's your future you need to consider, not theirs.