There will always be people that hire a professional writer for good content. Despite the doom and gloom that others mentioned, I don't think there's any major issue. There's still quite a lot of demand in the writing space, and in my experience, a lot of people took the AI route, but now they are coming back because AI ruined their website. And it's not an isolated incident, either. I see a lot of people doing this.
AI will always be an alternative for someone that wants writing, video creation/editing, even programming. But as mentioned, it copies other places, it uses those as inspiration, so it's not something unique.
The problem here is not that. Instead, OPs point is clear, AI checkers are a problem, because some buyers specifically rely on AI tools rather than the experience of a writer. It's not that often, at least for me, but it does happen. You will have someone that couldn't care less what you write, as long as it's not seen as AI by their tool. Last night I had a particularly interesting discussion with a person that said they want me to rewrite all their website content, which was fine, but it needs to pass their AI checker, without obviously telling me what tool is that. Who would agree to such a task that has a very high probability of a refund?