How do you ACTUALLY write a cover letter?

My cover letter is pretty generic, and I can’t find any actual good advice online about cover letters. Every reddit thread is mostly just people saying that cover letters are stupid and outdated, and that they just don’t write them. Although I agree, I still need to write them and I need a damn job. And then almost all the advice online is videos of insufferable recruiters with no soul behind eyes spewing contradictory advice and buzzwords.

What I gather is that cover letters should complement your resume and fill in the gaps, NOT restating or narrating your resume. I find that part hard, because even when I try to avoid that, it always happens and my resume pretty much tells my whole story. Chat gpt also kinda sucks for writing cover letters since it always just rewrites your resume in paragraph form. So, how do you actually write a good, engaging cover letter?