Disavow file opinions

I've always been one to ignore disavow -I still don't touch it really (unless something major) for main keyword under around 50 - but the last year since I've been working with more competitive keywords I'm unsure - I've seen sites that have ranked awesome when I didn't upload anything, and site's that wouldn't move unless I prune it and update. I get it's because of link profile blah blah blah, just wondering other people's experience.

I used to ignore disavow unless it was really bad. But now, with harder keywords, some sites don’t improve until I remove bad links. Some sites do fine without it. It depends on the site and its links. I don’t use it a lot, but I watch more carefully now.