Rather than competing on the product/network alone, Instagram employs dark patterns like allowing only a single link ("link in bio") to the wider web. Links in comments don't work, nor do older links-in-bio persist with their original post.
Facebook Groups is cannibalizing a dearly beloved two-decade-old backcountry ski forum ( turns-all-year.com ) because the user-onboarding is effortless, familiar, and integrates with other familiar walled-garden features. With the FB interface, the discussions are shorter-lived and the archiving of trip-reporting information is no longer effectively searchable. I don't know how an open-web forum with limited resources can compete against FB effectively -- suggestions are very welcome.
Strategies like these are designed to gently carve users away from the open web and gather them within the garden. While not impossible to combat, they are a stout challenge for sites in the modern era.