@Lily6 I require Verified ID for making reservations and you can too. Go to Manage Listing and to the left you'll see Reservation Requirements. Click on the box that requires Verfied ID. This doesn't mean guests with Verified ID will have reviews, but it is an extra layer of knowing who you are letting in the door.
The guest you mentioned who has been a member since 2014 might have signed up with the intention of using Airbnb and then didn't for whatever reason. Not necessarily a bad sign. Reviews are great, but the lack of them doesn't mean they will be a bad guest. I've had guests with no reviews and first-timers and they have been great.
Good Luck!