"If you use LLMs you're dumb and bad." You're literally a toxic gamer telling someone to "git gud." Imagine calling someone stupid because they said they use a tool to help them solve a problem. Are people who use calculators brain-dead idiots then?

Welcome to the real world. A lot of use are either disabled, or have been left behind, then shoved in the workforce so we can't resolve those issues, and drained of resources as well.

Demonstrably bad at research and math, yes. So don't use them for that purpose. A lot of work is being put into this area though, so it might change in the future.

Basic writing? That's such a broad task. As evaluated by what metric? One thing they're very good at is writing texts that sound like they're written by a human. If that's what you need, then they're great for the task. Especially so if you need a lot of it. I wouldn't say that the ability to write a thousand words per minute is a foundational skill for anyone.