I think you may also have missed the context that he/she used, as they described running an x509 CA first. In an organizational context, many organizations are

I think you may also have missed the context that he/she used, as they described running an x509 CA first. In an organizational context, many organizations are not going to jump to creating a novel CA type (SSH CA) when in fact regular x509 CAs are well known and the basis for much security, and many in regulated industries are using them already. Additionally, given that he/she is running an x509 CA, telling someone with that experience to study the fundamentals is not very polite. It assumes the author of the comment is not educated, but the very description of his/her use-cases are not simplistic ones. Engineering is all about tradeoffs after all.