Author here: you're for sure right -- it's not a problem with RAG the theoretical concept. In fact, I think RAG implementations should likely be specific to their use cases (e.g. our hybrid search approach works well for customer support, but I'm not sure if it would work as well in other contexts, say for legal bots).
I've seen the whole gamut of RAG implementations as well, and the implementation, specifically prompting and the document search has a lot to do with the end quality.
re: legal, I saw a post on this idea where their RAG system was designed to return the actual text from the document rather than a LLM response or summary. The LLM played a role in turning the query into the search params, but the insight was that for certain kinds of documents, you want the actual source because of the existing, human written summary or the detailed nuances therein
I've seen the whole gamut of RAG implementations as well, and the implementation, specifically prompting and the document search has a lot to do with the end quality.