Of course you have agency in government.

You do vote, don't you? You go and meet your politicians, right? You talk to your fellow citizens and organize among them, right?

I, as an individual, have put policy bugs in local politicians' ears just by showing up, shaking hands, making a persuasive case.

And that's just from a few years off-and-on involvement, no money changing hands, no campaign funding, etc.

I guess if you stay home and do nothing, then yeah, you have no agency.