FaceTime - its just for the sake of name & fame nothing else !
It requires high speed net or else you wouldn’t see it clear in video calls the in voice calls the sound wouldn’t be clearly heared
As FaceTime sounds famous because of the phone - iphone thats why it is working but I can say there are more other apps which is much more better thn this which you can use & let me tell you the Whatsapp video call & voice call is also much more better and good enough