You have to decide what "security" level you want, it depends on what you do with your phone (if you almost only phone, where is the danger?) - but that's not the point.
Apps thet I use are removed from the store from time to time. My solution is to always get the *.apk for an app I really want to use.
You can continue to install the apk for quit some time, even when Android tells you you should not (I install them from the computer with ADB).
For example I continue to transfer files with AirMore, although the app can't be found in the Google store anymore (but apparently still exists for iPhones).