Websites everywhere expend a great deal of effort to spread awareness of their brands across the Internet so that other websites talk about them in a positive light. The presence of web forums and blog posts voluntarily hosting links pointing to a particular site of interest is a strong indicator that the site should be regarded as an authoritative resource on its industry niche. This is why Google and other search engines look for these backlinks and take them into account when working out how highly a particular website should place in result pages generated on their services.
In addition to the raw number of backlinks without the "nofollow" attribute that a website has accrued, what each of the external websites hosting the backlinks are like in their own right can color the Google algorithms' perception of the website on the receiving end of that "link juice." If Google has perceived prominent issues with those external sites such as generally low quality, that could bring down the ranking of the website through no fault of its own. Of course, this would hypothetically allow malicious elements to proliferate deliberately harmful domains at the expense of a targeted website's SEO, but Google has a variety of automated measures in place to disavow the credit of any backlink-related scheme regardless of whether the scheme would help or hurt the target.
Since these schemes come in such a wide variety of forms that Google may not be able to block all negative link juice aimed at websites in general, site owners can defend themselves by going through a manual disavowal process using Google's services. A webmaster can always be assured that they have the means to block any juice they personally perceive to be harming their site. Nonetheless, they may not always be able to accurately work out whether enough of that juice would actually be considered "poisoned" by Google's metrics that disavowing those domains will do more good than harm. If a website's owner disavows much of the site's backlink profile because of backlink quality concerns, the site's ranking could possibly decrease regardless. For more information click here https://www.reddit.com/r/SEO/comments/e0vt00/ijustdisavowedlike280domainsabout90of_my/.