My Problem With Federalism

Whenever I hear people talk about federalism, or something like the paper we're reading this week for ConLaw about what number of sub-national units are optimal for promoting a dual-federalism balance between local and federal power, is: why do I care? When we talk of America's being "dangerously close to an omnipotent federal government," what is the danger? Specifically, given that it is ultimately elected representatives making the decisions at the federal level to exercise more and more power, why should we insist that the decisions about what sorts of powers will be exercised at the national level as opposed to the local level be made in a binding fashion up-front, rather than decided by the people as they go along? I see the categorical reason for wanting to limit the sum total of government power, but I'm not entirely sure I see a categorical reason for wanting to enforce certain rules about the vertical distribution of that power even if people don't like those rules.

Relatedly, I'm intrigued by the idea of what I call delegated federalism, which I suppose isn't really federalism at all but is really just when the central government grants non-negligible discretionary power to local administrative units. It strikes me that this sort of arrangement can simultaneously tap into a lot of the benefits of locally-customizable laws and avoid a lot of the problems with the "categorical federalism" approach we take in the U.S.. Basically the key point is that the decisions about distribution of power between localities and the nationality are made at the national level as a part of the normal political process. That way, if people actually want local authority, they get it, but you won't get the same kinds of lowest-common-denominator problems or civil rights problems we get in this country.