I was never confused.

The backward compatibility has a clean plan. For the bits that were complex changes, it was possible to do partial upgrades. From the beginning, the partial upgrade was in consideration. There was always early documentation, and you have access to v3 in alpha and beta all the time with complete documentation and complete guides. You also have standalone packages to start testing migrating bits of v3 to v2, like the composition API, class components, etc. It was one of the most seamless transitions I experience.