I’ve found it’s easiest to convince people when they can start small and work their way up. I generally introduce them to one application at a time in roughly the following order.

1. Easy slot-in free replacements, which have pretty much the same quality, such as Google Search, chrome, messages, and Drive.
2. Replacements that are still fairly seamless, but either require more effort or are less polished, such as Google Photos, YouTube (switching to NewPipe), and Keep.
3. Things that require significant effort, a small cost, and/or the ability to self host, such as Android -> Graphene (effort), Email (cost), and Contacts/Calendar (cost or self-host).
4. The annoying things that don’t really have a proper replacement elsewhere. Maps (specifically the public transit part and navigating to individual addresses instead of blocks), Assistant (I actually just stopped using this category of application completely), and Pay (also stopped using this, since they’ve got a duopoly, alongside apple).