The links weren't coming from blogging platforms, so NOFOLLOW isn't relevant here.
I'm aware that there are always algo updates, what I meant was a BIG one that is making a lot of waves with other webmasters.
Second of all, you may have experienced a drop, but what have you done so far to ascertain that it's links that are the problem? You dropped rankings on some keywords, but what about pages? Who replaced you? What are your engagement metrics like?
It might seem like I default to the noob "negative SEO" reason, but its really not. Like I said I never bothered with disavowals till now, and I am quite aware that there is a ~5% chance that the drop is unrelated to this issue.
BUT some of the links are now coming in from #*$! sites, and others try to popup different things, auto play strange videos and the like. And this info is just from accessing the google cached versions (since I don't trust them). A lot of the sites also don't show up on a site: search which is always a little red flag to me.
I agree that a lot of weird links are usually from dmoz scrapers and the like, but this has gotten past that now.
Engagement is the same, some CTR have even gone up a bit. I am also in the midst of solving another possible duplicate content issue, which might also be responsible. One possible competitor has gotten a 3x jump this month according to SEMRUSH, so he might be on the same BH SEO + Negative SEO package from a shady agency...Another competitor is also Chinese based, so just as they have no qualms about stealing content, images, and the like, I assume that they are open to any kind of SEO boost....
Again this was not meant to get into those usual "competitors are going after me" debate, but more to understand what the current climate is on actively disavowing links. Like I said I'd never done it till now, because my reasoning was that I'm not doing anything wrong, so I don't need to use it. But I've been reading that more and more people use it on an active basis.