Lol it's network core. Postpaid users on Verizon branded accounts affected. Most MVNO's just fine (checked US Mobile and Visible, different cores... and they are working fine on the Verizon towers)
As I've said elsewhere, never underestimate Verizon's incompetence. A couple years ago they shut down vtext service which also happened to host their UAprof's for most Android phones. Without a working link to these descriptors, those devices would download any MMS (pre-RCS picture messages) in compatibility mode at the lowest resolution.