MMS Text will not send using Iphone 11 connected to Xfinity Wifi or any other WiFi

After researching some say that cellular data needs to be turned on. So what is the point of the Wifi? 

If this is the case, when will Xfinity Mobile remediate this?

Is there even a plan in place to remedaite this so that we dont have to use data to send a MMS?  

At this point I just use WhatsApp to get the MMS to the recipient but it shouldnt be like this.