Sure, there's a gajillion of those processors all over the world, and they somehow all work with mastercard and visa.

Diners club? Well.. "it depends". Many don't work with it.

Indian, russian, chinese, cards? Maybe in india, russia and china, but you shouldn't expect it to work "everywhere" like visa and mastercard. Same will be true for EU cards for quite a few years, especially if the system gets fragmented into many different companies using many different systems, and you'll always wonder if your german card will get accepted in Algeria like your friends' french card is.