For years I synced my Google Calendars with MacOS’s calendar app without any issue with syncing. It should work fine.
So I would think about exporting your events from any iCal/iCloud calendars and importing them into Google Calendar if you are going to use an Android phone.
File / Export from the calendar app on MacOS, choose “Export”, and it should create an .ics file that you can then import into Google Calendar. When you are satisfied that everything is in the Google Cal, then you can delete the calendar from the Mac Calendar app and set up calendar syncing from the Accounts tab of the Calendar app preferences. Edits and additional events on the Apple Calendar app should then sync to Google Calendar and show up on the phone.
And in case you have an iCloud calendar (and would like to keep it there), but still want it to show up on your Google calendar, that’s quite simple too.
In Calendar app, right-click on your iCloud calendar and select Public Calendar. Once that’s selected the share URL will be displayed below. Copy that.
In Google calendar, click on the + next to “Other calendars”, select “From URL”, and paste the share URL.
There is no step 3.
It would indeed be nice if subscribing to the iCloud calendar would require first authenticating with iCloud credentials, but that’s not the way the protocol works.