While it's true that there will always be special interest groups, it's not true that the current situation is even close to "more or less the best it can get". There's too much power in far too few hands due to capital accumulation. This is not a natural law.
I was not arguing that this is the "best it can get", just that there is no structural answer to these challenges. There's no way to setup our institutions such that they cannot be influenced by interest groups, so the only thing to do is be vigilant and fight the good fight.
If you look at the whole range of regulatory capture we see, it's not just billionaires who have managed to get what they want, it's all sorts of interest groups who have succeeded in enshrining the interests of incumbents into law.
Good for you for being riled up about the concentration of capital, but addressing that is nowhere near a magic bullet for addressing regulatory capture.
There is no enduring structural answer to this problem, it is fundamental to democracy.
The only answers are to struggle for our goals in the political and cultural arenas to hope to marginally improve the situation.