[CWuestefeld]

The kind of problem described in the OP doesn't seem orthogonal to ACA. It looks to me like the problem is part of the adjustments that the market has made in response to the regulation. One of the biggest tools used in differentiating between the various levels of ACA marketplace plans is the breadth of the network they allow access to: getting more providers to accept your plan will cost you additional money.

It only makes sense to at least postulate that the converse is true as well: if you find yourself stuck out-of-network, it's because these regulations created an environment where the insurance companies could do better by eliminating the providers it partners with. So it's reasonable, at a first approximation, to guess that this problem is the result of ACA.