I write what I consider to be awesome cover letters, if simply because recruiters tend to mention something from them when they reply. What I wrote was clearly read in full.

ChatGPT produces this bland and generic resume summary. I wish it could generate something I thought awesome, but it cannot.

I would note that my teachers would be appalled at how casual and filled with puns and jokes they are, so it is not by any means the "Dear Hiring Manager" kind of cover letter.

Or is the worthlessness of cover letters killing cover letters?

Well, yes and no. Most of the cover letters I've seen are too general and don't add any value.

But it seems (tech) companies still use them and it might work for candidates with less obvious experience to at least try to get the first interview.