Somewhere around three or four, Google starts visiting a page noticeably less often, and content that's never linked at all might not get crawled through navigation no matter how deep it sits. TechySEO maps the actual link graph of your site to find pages buried too deep, pages with no inbound links at all, and content sitting behind a "Load More" button that's invisible to a crawler entirely.
Google doesn't crawl your entire site on every pass, it allocates a limited amount of attention and spends it according to its own priorities. A page sitting four, five, six clicks from the homepage falls further down that priority list, which means changes made to it take longer to register and rankings respond more slowly to anything you fix there. The pages that actually matter to the business should be the shallow ones, not wherever they happened to land in the nav.
Orphan pages take the same problem further. A page with zero inbound internal links might still get discovered through the sitemap, but discovery isn't the same as being treated as important. No internal links means no internal link equity, and a page with no equity behind it rarely competes well against pages that have some. Every piece of content published without a deliberate internal link plan starts the race already behind.
Mapping the actual link graph is what turns "I think some pages are buried too deep" into a specific list of which ones, and what to link from where to fix it.
Built from the actual link graph the crawler found, not from what the nav menu implies.
Build the real link graph and find the orphans, the buried pages, and the content stuck behind a button Google can't click.