Classic has a VERY small team of mostly database folks... there is/was nothing enormous about the project.
The only thing affecting BfA is the current dev team led by Ion. They have been running the game int the ground since WoD...
I'm all for trying to find "the next best thing" and moving away from things that don't work. But Blizzard has been throwing the baby out with the bath water for several years.
Truth is, Ion has no idea how to make WoW better... he is firing shots in the dark to maybe hit on something good. In reality the REAL problem with WoW isn't what they have added so much much as what they have taken out. Yes things like LFR, Dungeonfinder, Titanforging, CRZ, and shared tagging have deeply hurt the game... but so has undermining the systems that made WoW great in the first place. It's been gone over countless times so I won't bother other than to mention a few... the importance of guild, group content actually requiring groups, server community/reputation, rarity of gear, importance of professions, depth of skills including the need for CC, mana management, eating and drinking, etc.
It's easy to look at that list and see what was taken out... the social aspect, the reliance on other people to progress in game. Crucial in an MMORPG... modern WoW has morphed into an MMOARPG... and the whole massively multiplayer aspect is dwindeling to moderately multiplayer. IN fact, the game is becoming more of a massively solo player game wher eyou happen to see other people from other servers you can't really interact with.