Comment on Technical Support by SEO Dave.
The recipe site was partially automated, used some recipe databases to pull the recipes from and import them into WordPress. Not worked on backlinks to that site for years, so wouldn’t expect it to be any where near fully indexed.
Means the content isn’t unique, that’s a full indexing issue.
Also there’s a lot of title tags that are very similar like Chicken Recipe 1, Chicken Recipe 2, Chicken Recipe 3… which is also an indexing issue.
A well thought out silo SEO link structure per se won’t increase a sites indexing. What it does is better target the anchor text of internal linking which if a page on a site is indexed will suggest to Google it should be ranked for phrases related to the anchor text to/from the page.
Silo SEO will make indexing of some parts of a site better and others worse. Take this site, a majority of the content has an SEO niche to it, but there’s a small amount covering product reviews.
For example I have a post about Direct Line Car Insurance, if the linking structure was evenly shared internal links to all posts, the insurance post would have as much link benefit sent to it as the post that starts the SEO tutorial. That means the insurance post is as likely to be indexed as the SEO tutorial post.
With my current silo SEO linking structure, because I don’t have many product review relevant posts the insurance post will have significantly fewer internal links than the SEO tutorial post. So the insurance post is less likely to be indexed relative to the SEO tutorial post.
With 300,000 webpages it’s almost impossible to fairly link to every webpage, you have to prioritize.
I assume the most commented posts are the ones with most traffic, so my silo SEO widget is going to pass more link benefit to the parts of the site with the most comments and in niches with most content (on this site the SEO niche). On top of this I add manual links to really important content, you can see my navigation menu below the header, it’s sitewide and links to the most important parts of the site.
With a 300,000 webpage site you should work on backlinks to important parts of the site not just the homepage. If this were a huge site I’d work directly on backlinks to the SEO tutorial sections and the Stallion Responsive theme sales pages. On the recipe site I’d work on backlinks to important categories, so if there was a lot of traffic to chicken recipes I’d gain backlinks to those categories.
With huge sites you have to work on them like you are indexing multiple domains, you will need the backlinks equivalent to dozens of smaller sites to get most of it indexed.
BTW I don’t use DA Authority, it’s a measure created by Moz and has no more value to me than a guess.