Link building has changed so much in the last 10 years. If someone tried to use the same tactics we used a decade ago for a client, they would probably do more harm than good. Backlinks are still a ranking factor although no one agrees on how much weight Google gives them.
One thing we do know is that only links from relative, quality websites have any impact. Years ago, a link was a link, but today, publishers are disavowing links from spammy websites. In fact, people are seeing their competitors get them backlinks from pornography and gambling websites when their site has nothing to do with these industries. Publishers have to disavow the links to avoid a Google penalty.
Spammy directories are also a thing of the past. There are industry-specific directories, such as Justia and FindLaw for lawyers. These directories are may help with local SEO, but their main value is that consumers use them and they may drive traffic to your website.
Submitting to article directories is out. At one time, you could write one article, spin it and them submit an original article to multiple directories with a link back to your website. The articles were very poor quality and Google now views article directories as a home for bad content. Today, people guest blog, submitting one high quality article with a link to an authoritative blog in the same niche.
Buying links is also out. Getting a hundred links in one week from irrelevant websites looks very suspicious to Google. Stay away from anyone who sells links from their private blog network as well.
The best backlink building strategy today is to create great content and post it on your blog and social media accounts. People will naturally link to informative, funny or engaging content. Content isn't just articles anymore; videos, podcasts and infographics are also link-worthy content. For more information click here https://www.reddit.com/r/SEO/comments/bk4m99/ihavebeenoutofseoformorethan7years_how/.