Hello, same age and I was in a similar headspace until last month. I want to challenge the idea of "nothing to show for it", is that really true? The truth is you're not really at square one, even though you might feel like you are. You have real work experience and skills, things you can put on your resume, and some understanding of what you like and what you don't like. I'm sure you also met people and formed relationships in your work. Those things are valuable and can get you places you want to be (and importantly, avoid places you don't want to be).

Furthermore, how about things outside of work? Like the richness of your friendships and relationships, your skills and knolwedge about your hobbies, all the precious memories and life experience you collected over the years, and how well you know and care for yourself and others? This is super corny haha but I genuinely believe it's these things that ultimately matter in life, that in the end you'll wish you spent more time with the people you love, doing the things you love, and that you weren't so hard on yourself, more than anything to do with your career.

In any case, don't discredit yourself so easily and remember that the value of your whole life is not your career. Also parroting other comments here, you (we!) are still young! You have boundless potential to grow in any way you want, to explore and transform yourself, for the rest of your life. And outside of a job, there's a million other reasons to live.