I don't really understand why.
I can describe the PCs in my 4e game, and I'd be surprised if the descriptions caused any deep puzzlement: fighter/cleric, demigod ranger-cleric, invoker/wizard/divine philosopher/sage of ages, sorcerer/bard who is an emergent Primordial, questing knight paladin of the Raven Queen who is a Marshall of Letherna.
The only thing there that you mightn't recognise is the placename Letherna - the realm of the god of death.
I can talk about the abilities they use - "Blazing Starfall" and Demonsoul Bolts for the sorcerer, Enfeebling Strike for the paladin, Twin Strike for the ranger, weapon AoEs for the fighter, spells like Twist of Fate or Hand of Radiance or Tide of the First Storm for the invoker - and they shouldn't be any more or less opaque than spell and ability descriptions from any other version of D&D.
I'm puzzled as to what the "completely changed" parlance was. Acronyms for ability durations (EoNT, SoNT, etc)? Role labels (striker, defender, controller, leader)? As someone who has played B/X, AD&D and a little bit of 3E, I didn't feel the parlance had changed very much at all. Maybe I have a good tolerance for jargon?
That said, when I read a 3E or PF thread I sometimes have to Google and acronym or a piece of terminology to work out what is being talked about. But that's just part and parcel of not being familiar with a particular game system.