Internal linking is treated as something you do while writing a post. At scale it is an asset allocation problem: you are deciding where the authority the site already has should go.
Decide which pages you are funding
A handful of pages should receive disproportionate internal links because they are the ones you intend to rank. That is a deliberate choice, and on most sites it has never been made — links are distributed by whatever writers happened to remember.
Templates outweigh editorial links
Navigation, footers and related-post modules generate the overwhelming majority of internal links on any large site. Auditing editorial links while ignoring the template that emits forty thousand identical ones is auditing the wrong thing entirely.
Old content is the underused inventory
Every published article is a place a link could go. A systematic pass adding relevant links from existing pages to priority pages costs no new content and is usually the fastest ranking improvement available on an established site.
Build the process into publishing
Requiring every new post to link to two existing pages, and one existing page to link to it, compounds automatically. Without that rule, internal linking is a project someone runs once a year and it decays in between.