Compared to Google, moving out of icloud is mostly pretty easy (mail, photos, contacts, calendars, files). imessages, safari tabs and bookmarks, and health data less so, but not sure there are many others from Apple.

Proprietary programs that store their data in icloud are harder to export but that's the problem of the app vendors. This includes Apple office apps like Pages or Numbers, but for them at least you can use applescript to export those files in non-apple formats. Easier than Google, TBH.