I have almost never had an LLM not do the task I wanted. Either I'm asking it very easy things (not really, you definitely couldnt Google the entire task of what I wanted, although obviously each tiny subsection you could), or it's important to scope what you're asking for well.

But as a general statement, you cant just Google a comprehensive summary about beta glucans from chanterelle mushrooms, dosages, cooking methods, immune benefits and processes and get a 10 minute read about exactly what you asked for. But with Gemini deep research you can.