I believe there's some confusion with your definitions. I guessing you're referring to the default
Android email app that comes on most Android phones.
Gmail is Google's email service, and whomever told you the Gmail app is no longer available in the Google's Play Store is incorrect. (Although that's most likely not the app you're attempting to ask about.)
https://play.google.com/store/apps/details?id=com.google.android.gm
The Android default email app, if that is what you're asking about, is not in the Play Store. It's installed as an OEM app and should still be on your phone. There are however plenty of very good third-party alternative email apps in the Play Store. I like K-9 Mail, a lot of others prefer AquaMail, and quite a few people have recommended Blue Mail. But they generally have more features with busier interfaces and as you mentioned you prefer a simpler email app the Android default email app is probably a better option for you. Again, it should still be on your phone. If its icon isn't for whatever reason somewhere in your home screen it'll be in your Apps menu and you can just add it back again from there.