The two main issues now are 1) PBNs are TOO popular (too many people are out there looking for them), and 2) SEO is now a two-part issue (ranking keywords to get a site to a top position, and proving the site is valuable to visitors, via good user experience, to keep the site ranked).
Nargil and others have pointed out how difficult it is becoming to get 'first class' PBNs, or expired domains with strong TF and RD plus a clean history, and how prices to buy the best ones are often going through the roof. And unless you put long articles, videos, giveaways or other value on your pages, expect your site to later drop in the rankings even if you did the backlinking right. If the OP is wants to back into SEO, read the most recent stickied threads on BHW, and posts by bloggers like Brian Dean at Backlinko.