I have the same issue, I can’t text pictures to anyone using android phones (verified they have no issues on their end) but I’m having no other issues with anyone else sending photos with Wi-Fi OFF / Cellular Data ON, just updated my iPhone XS Max (10) today never changed any of the settings but I double checked and the SMS/MMS and Group messaging are still on. So I should be able send it as it would be going through carrier services and not iMessage or Wi-Fi anyway. Reached out to my cellular provider and we did all the troubleshooting and updating on their end, the Cust Rep had to transfer me to supervisor or technical supervisor and the call got dropped while I was on hold. So I’m going to have to call back tomorrow.
It just seems like a really strange issue overall because everything else is working fine, my data/ internet is working great with no Wi-Fi. Calls are fine. I’m hoping they will figure it out soon.
Hope that made sense, I’m not really a tech person but I would be interested to know if anyone else is also having this oddly specific problem or gets any further info on how to fix it.