I'm pretty sure that Matthaios, Markos, Loukas and Ioannes would not recognize their own names in the present-day English pronunciations (well, Mark and Luke might, but John would certainly not).

Come to St. Louis where everyone mispronounces the French street names. Doug Crockford coined JSON as "Jason", but nearly every developer I've ever run into says "jaysawn", so that's how I say it too.

And? That's only relevant if it's their own name, or potentially if something falls under the purview of the Académie Française, and even then, that requires you to care what the Academy thinks.

There is more than one canonical way to pronounce things, even names. For example, what's the correct way to pronounce Arkansas?

The real issue here is people trying to assert there is only one correct way to pronounce it.

Virtually all names are pronounced differently from how they originally were.

So are the names of countries but people rarely pronounce them as they are in their country of origin.