Maps -> OsmAnd~
The usability of OsmAnd~ will depend greatly on the area where it is to be used. It can use a host of map tile providers and/or vector maps, the detail level of these varies from very good to hardly any. I use it in Sweden where it generally works fine.
Waze -> ...
OsmAnd~ can be used for navigation but it does not offer live traffic updates.
Gmail -> my own mail server + K9 on Android
Gmail is more or less equivalent to a mail user agent, right? Mail is an internet standard which has been around for a while, long before Google was launched from a scruffy server under a desk. With a bit of luck mail - or some other open protocol like it - will be around when Google has gone the way of so many of its predecessors.
The list goes on:
Google Search -> a private Searx instance
Google Drive/Documents/etc -> Nextcloud on a private server
Google News (remember that?) -> News application on the above mentioned Nextcloud server, using either the web front or one of the Android apps available on F-Droid.
Youtube -> private Peertube instance on the already mentioned server
Facebook, Twitter, Snapchat, Instagram -> No need for such
Whatsapp -> private XMPP (ejabberd) server using Conversations Android client, using OMEMO encryption. Also using Telegram app from F-Droid.
Spotify et al -> Airsonic on that server I mentioned, feeding off my private collection and also serving internet radio stations (which it also sometimes uses to update the private collection). Using Dsub (from F-Droid) on Android, the web interface on PC's. The same collection can be reached through a host of MPD instances scattered about the place, these are controlled through MPDroid or M.A.L.P (both from F-Droid). There are also a few Kodi instances, controlled through Kore (from F-Droid).
The list goes on.
There is no Google-proprietary code on any of my Android devices yet they provide me with all these services.