MicroG can replace the Google Play Services requirement for Google Maps. To download Google Maps without the official Google Play Store client, you can use the free and open source Aurora Store:
Google Maps is marked as dependent on the Google Services Framework, but it clearly doesn't use the same map tile rendering system that MicroG uses. I guess Google Play Services is only used for the logged-in features, which privacy-conscious users would avoid.
On the phones I have tested Google Maps works with Google Play Services turned off.