The "in-network" thing is anyoing. As long as the place has a license and hasn't been a issue, they should be "in-network".
Having insurance tied to a job doesn't help either. if you/family member needs specialist care, so you find a fantastic doctor, but oops your job changed insurance provider and now your doc is out of network.
Complaints aside, if you're actually having trouble finding a dentist; go to your insurance's website, they probably have a "find a dentist" tool or something.
I hear you. The challenge is what the insurer is willing to pay for the services the dentist provides. At the end of the day, the deal is "we are bringing more patients to you by being in our network, so you'll take less money for your services in exchange." And sometimes the numbers just don't make sense for the doctor to accept.
This is why dentists in the US decided to not make themselves part of the same system as other medical doctors-- The ADA vs AMA. They get to make their own rules and more importantly, deals to get paid.
And full cash money rules over whatever any insurance company decides to pay you.