Check your robots.txt file. Make sure you learn how to hide content you don’t want indexed from search engines and that search engines can find the content you do want indexed, too. (You will want to hide things such as repeat content, which can be penalized by search engines but is still necessary on your site). You’ll find a link to how to modify the robots.txt at the end of this article.
For Search Engines, backlinks help to determine the page’s importance and value (i.e. authority). Historically, the quantity of backlinks was an indicator of a page’s popularity. Today, due to the way backlinks are evaluated based on different industry-related ranking factors, it is less quantity focused and more about the quality of sites from which the links are coming.
As Rich White also said in the comments, just because PR scores are no longer visible doesn’t mean PageRank is a thing of the past. It still matters a lot. PR remains one of Google’s 200+ ranking factors. You need to receive links from quality, on-topic web pages and then properly manage that PR through your website through siloing. These are powerful things you can do to boost your pages’ relevance in search.
Matt, as you know, I was kind of annoyed when you suggested sculpting to a room full of SEOs back in 2007. We’d been told over the years to do things for humans, not to overly worry about having to do stuff for search engines — and suddenly, here you were suggesting that SEOs could flow PageRank to their most “important” pages. I’d figured Google had long since been smart enough to decide for itself what percentage of a page’s PageRank spend to assign to a particular link. That assumption didn’t just come out of the blue — it came from things Google had hinted at over the years. So being told to start overtly flowing around the PageRank? It seemed counter-productive.
If the algorithm really works as Matt suggests, no one should use nofollow links internally. I’ll use the example that Matt gave. Suppose you have a home page with ten PR “points.” You have links to five “searchable” pages that people would like to find (and you’d like to get found!), and links to five dull pages with disclaimers, warranty info, log-in information, etc. But, typically, all of the pages will have links in headers and footers back to the home page and other “searchable” pages. So, by using “nofollow” you lose some of the reflected PR points that you’d get if you didn’t use “nofollow.” I understand that there’s a decay factor, but it still seems that you could be leaking points internally by using “nofollow.”