There have been studies that report the same thing: using an AI for too long actively makes you dumber.

I am starting to appreciate all the times stackoverflow people told me my question itself is wrong and I am stupid.

Well, the first part mainly.

There are things LLMs are genuinely useful for.

Transforming text is one. To give examples, a friend of mine works in advertising and they routinely ask a LLM to turn a spec sheet into a draft for ad copy; another person I know works as a translator and also uses DeepL as a first pass to take care of routine work. Yeah, you can get mentally lazy doing that but it can be useful for taking care of boilerplate stuff.

Another one is fuzzy data lookup. I occasionally use LLMs to search for things where I don't know how to turn them into concise search terms. A vague description can be enough to get an LLM onto the right track and I can continue from there using traditional means.

Mind you, all of that should be done sparingly and with the awareness that the LLM can convincingly lie to you at any time. Nothing it returns is useful as anything but a draft that needs revision and any information must be verified. If you simply rely on its answer you will get something reasonably useful much of the time, you will get mentally lazy, and sometimes you will act on complete bullshit without knowing it.