If Activision owns Bungie

They don't.

why is WoW so successful and pretty much microtransaction free while Destiny 2 is not?

Numbers suggest Destiny 2 is successful, so whether we like it or not, it still sold. With that being said, WoW uses a subscription to gain cash, where as Destiny does not. If we had to pay XYZ a month for Destiny we would likely see Eververse go away, but it becomes a very different question.

but even game time can be purchased with in game gold for a reasonable and realistically achievable price vs amount of play time required to earn it.

WoW also has less overhead. Like, Bungie has to deal with Sony/M$ when they release a patch and that costs money. Blizzard can release as many patches as they want, as quickly as they want, without any real issue. I also believe the gold stems from the games age, as gold has real world value, and so much of it is out there that the only way to make the economy work is to take some of it out of the system.