I tend to agree. Skill files become less useful as developer skill increases.

As a skilled developer my repetitive instructions are mostly one or two sentence phrases for staring something like a highly-interactive planning session, or a self-supervised implementation session with my preferred setup of implementation and review subagents. I can specify those out by hand, or save a couple keystrokes with a tiny skill file.

But if you are not a software dev you might lack the vocabulary to tell the agent what you want. If you don't know what tenant isolation is, chances are your app will have a broken security model because you can't ask for it, and probably won't think to ask the agent for a security review either. Skills can mitigate a lot here