Right, that's basic Public Choice Theory, and it holds in all cases. With respect to transparency, there are really only two potential scenarios:

1. A closed an opaque political system operates outside of direct public view. Those with the strongest interest in influencing it invest efforts into gaming the system, co-opting its participants, and manipulating it through back channels also outside of public view. Those who suffer from the negative externalities of political intervention have no visibility into the process that created them.

2. An open, transparent political system operates in full public view. Behavior of politicians, relationships with special interests, and their explicit votes are all public record. Those most motivated will still invest more heavily into influencing the political process, but those who are affected by negative externalities have visibility into what's creating them, and if they should become motivated to act, e.g. if the effects of those externalities hit a tipping point, they have the knowledge and means to do so.

The perfect world that you're envisioning depends on politicians being presumptively trustworthy, well-intentioned, and having perfect knowledge of what their constituents' interests actually are. None of that is possible, and shielding politicians from direct accountability will only serve to make them more beholden to the small set of interests best suited to navigating their way into the system.