How do you migrate a tube to a new script without tanking your rankings? A migration touches every URL, and a botched one erases years of ranking through broken redirects or a crawl that finds a mess. The new platform might be genuinely better, but the risk keeps people stuck on worse ones. For anyone who has actually done it on a content-heavy site - how did you preserve the SEO?
that is how migrations die. the equity is attached to your urls, change them without perfect redirects and it is gone. either keep the url structure or map every old one to its new home.
and build that map from a full inventory of your indexed urls, not from memory. the ones you forget to list are exactly the ones that break quiet.