Apple will use it's dominant position to create lock in like how they did with iMessage instead of cooperating with other platforms on a common standard.
Oder friends and family are surprised when they want to video call over Facetime and find it hard to believe other people's phones don't have Apple apps.
The telcos specify the size limits of MMS messages. iMessage has much higher limits in most cases, so iPhone has to use reduce the quality of the pics/videos to reach the lower size limits for sending to non-iMessage recipients.
For the telcos, why would they upgrade their size limits for MMS - it's just a cost centre for them. They probably make more by selling more iPhones as well.
Android implemented RCS and Apple dragged their feet in implementing the standardised platform such that high quality messaging was seamless and agnostic between brands
The iPhone needed to reduce the quality of pics/videos to non-iMessage recipients because Apple didn't support any other form of non-iMessage messaging.
And of course there's no encryption standard.
Maybe its your phone going overseas and not working correctly.
I buy an Esim for countries I visit, usually before I go. Add it before the flight, sometimes in the country.
List of countries I have worked with: Singapore (Roaming), Indonesia, Malaysia (I may have been roaming in Malaysia) I can't find the esim info, Thailand, Australia, New Zealand, India (Maybe i was roaming, can't remember).