I’ve never actively looked for work. I’ve never written a resume or a cover letter in my entire life. I’ve never been on a job interview

My local unemployment office has free classes that teach all of these things. This may not be the case where you are, but you should check your local library, community college, etc for a class on resumes and job interviews. It will allow you to meet other unemployed people who are in a similar hole that you are in, where for whatever reason they just never developed these skills, and it will let you practice doing them in a low-stress environment. Don't stress yourself out about the time you feel like you wasted in the past - what's important is that you're not wasting the present.

After that, the only way to get good is to fuck up enough times that you stop being bad. I would say I'm pretty good at job interviews at this point but I've had some really awful ones, ones where I got asked questions where I didn't even know what the interviewer was talking about, ones where I said some shit that I only realized after I said it sounded really bad in an unintended way, interviews where I would have given anything to just evaporate from existence rather than continue dragging it out. But I had those shit interviews, and then I had a hundred or so pretty good interviews afterwards.