dave2008
Legend
That's an unfortunate retcon there in Mearls answer on top top of the already extant retcon regarding "oinoloths" in MToF.
Anthraxus is an altraloth, formerly an arcanaloth (per the 2e 'Pox of the Planes' article) prior to his transformation.
I'm disappointed that as 5e seems to be genuinely trying to appeal to fans of prior settings and make reference to them in 5e content, it's retconning a pretty massive amount of the lore from those settings.
I am not sure what else you may be talking about, but given the vast amounts of D&D lore, I think this change to oinoloths and Anthraxus is not a big deal.
Hell, i'm still miffed they retcon'd him in 2e (I think) with the General of Gehenna being the new top dog. I like the 1e MM2 version of Anthraxus and that is about it. I really didn't like all the lore BS they added in 2e and 3e.