Once you start paying content creators directly (with the condition that there are no ads and no tracking), then ad networks have nothing to do with the whole situation.

matt4077 might be right actually; those who choose to pay to avoid ads are probably not broke and thus more valuable ad targets, so (some?) content creators will get greedy and double-dip by producing content steeped in product placements or equivalent. That, in turn, would undermine the idea and adoption by the willing-to-buy-out-ads segment would be low.

In-content ads are regulated in many places. You can't do it unless you explicitly mention that it is an ad.