Loosely, LLMs give plausible responses. And LLMs are really good at writing confident-sounding responses.

LLM output is as if someone is replying with the sole purpose of appearing helpful and knowledgeable.

I wouldn't trust opinions on LLMs from people who are entirely positive or entirely negative: the technology is just too mixed for that. I'd say it's useful for someone to have had a bad experience with LLMs (e.g. LLMs being confidently wrong), as well as making use of LLMs for things they're powerful at. (e.g. "small" programming tasks).