The difference is, back in 1978, if you dropped scaling hit points, added skills, and gave everyone access to magic, you didn't claim you were playing "D&D"; you were playing RuneQuest.
I agree, RQ, T&T, aruduin, et al they are all house rules of gary and daves d&d. I don't think anyone begrudges someone taking d&d and house ruling it to hell, what I'm hoping is wotc's plan is to re-present and represent d&d
but encourage people to make harn/arduin/RQ with the same set of rules. . If the default character classes in thr PHB look like and play like ad&d, who cares if some other dude plays a dragonborn psion? Dave had balrog characters in his campaigns, strategic review and dragon are full of odd classes that never made it into the original PHB.
I'm no wotc fanboy (don't care much for 3e, never played 4e). Wotc seems interested in supporting peoples home campaigns and no longer pushing an official version (I've read the will be supporting forgotten realms before tieflings, dragonborns and spell plagues for example as well as supporting players who want all that). Isn't that the best? Instead of trying to pull a TSR and say "this is the offical way to play the game" they seem to be saying "here is the basics of d&d and here are options for DM's and players for their home game.
As long as they get the basics right, It would be like one guy using elderitch wizardry, some other dude using blackmoor, some other guy using a rule he found in dragon mag. All d&d, just flavored to their home campaigns like it should be.
I play od&d, so 5e has quite a hurdle to overcome as my version already has rules for masscombat, nauticle adventures, air combat, hex crawling, barony building, hirelings and henchmen, underground exploration etc, so they might not sell me anything--they'd just need to reprint all the adventure modules. Maybe someone at wotc will write a good exploation module? Mayby I'd buy it.