This dentist had the balls to drop out of network, probably because he's good and has enough patients to not cave in to the absurd demands of insurance companies (they pay far less than a FFS practice, just FYI)
So you decide to drop your good dentist, and go to lower quality ones, just because they are in-network (guess what? these guys actually need to drop their fees because they don't have enough patients otherwise)...and then you find out that these new dentists are lower quality and need to prescribe unnecessary procedures to make ends meet
Solution: like in any other field, value quality over price, go back to your old dentist.
It's like Apple charging more for an iPhone simply because it's higher quality and is time-tested, of course if you buy cheap cell phones they are worse and screw you up some other way.
The real problem is insurance companies here, they are screwing both dentists and patients extracting money in a place where they shouldn't be (why do you need a middleman between a doctor and a patient anyways?)