I also found it very difficult to DeGoogle. I've documented my efforts here: https://www.augmentedmind.de/2020/03/15/without-google-servi... (that article links to a companion article specifically for replacing Android apps made by Google). I'm fairly convinced that noone who reads these articles (mine included) will do anything that is written in them. Powered by laziness and "I don't care" syndrome :).
In the end, my practical recommendation is to just reduce the number of services - not necessarily get down to 0. You'd be at a loss. There is no good GMaps alternative (not in Germany anyways, the level of detail of the maps data and/or search results of any competitor is poor in comparison, including HERE WeGo or OSM). Same for web search / google.com. I have experienced many times that DDG/Startpage/Bing would not find what I was looking for, then I switched to Google, and found something relevant right on page 1.
Other services, especially those with standardized exchange-import/export formats are easier to migrate, though. For instance, GMail, including calendar and contacts sync, or using another provider for your files (GDrive).