I do not sign in to a Google Account on the phone, because I dislike the idea of link a device to an online account.
Without a Google Account, I cannot install applications via Google Play Store. Thus, I use F-Droid (free and open source) and APKPure (apk files identical to those in the Google Play Store) to install applications.
I also use some preinstalled applications, for example, calculator and Google Photos (with backup & sync turned off since I do not sign in to a Google Account).