You can simply not sign into a Google account, and Android lets you turn off more tracking than iOS, which won't even let you get your location without telling Apple. No need to install a custom ROM.
If you want to use an inferior Gmail client similar to the iOS Mail app, you can simply access Gmail using a third party mail client on Android exactly the same way.
The difference is you don't have to give your location to anybody on Android, while Apple makes you give them your location. You don't have to tell anybody that you installed an app on Android, while Apple knows every app you've installed and when you used each one.
FYI, Google maps works without you needing to sign in (iirc it doesn't even need Play services, so it works with de-googled custom ROMs). Though this is an exception rather than the norm.
On iOS you can have the above without giving them your location 24/7