The idea of a representative democracy is that in contrast to a President who elected nationally, there will be Senators elected from the various states, and representing the interests of their states, and representatives who will likewise be elected from only a part of a state, and represent and look out for the interests of that part of their state.
Throughout the history of the Republic, this has worked pretty well. Critics may argue that at times it has led to the funding of projects of limited value (such as a highway interchange that will serve a town of a few hundred people or a research project on a topic of dubious importance but directs funding to a particular college where the research will be carried out,) but in fact this has always been as conventional wisdom had it, an important part of government. Standard wisdom in an earlier day was that "Political hacks used to say pork was the political grease that lubricated legislative deals."
This meant that it was possible to get enough votes for key legislation by including yes, some pet projects (though one man's 'pet project' may be another man's lifeline to the outside world; hardly any of the infamous 'pork' legislation did not in fact provide at least some benefit even if it was to a relatively small part of America; there are frankly a lot of towns that could be benefited by a new post office, a road paving or some other investment in infrastructure.
What we see today, instead of members of Congress who are able to effectively represent their district and in the process get the necessary funding for improvements, are members of Congress who may not even be beholden to their districts at all. Big money has (especially since Citizens United) moved into the political arena in a major way, to where even members who raise millions of dollars on their own, may have it matched by groups that have one or two anonymous donors. In 2010, these groups were almost entirely working on behalf of the GOP, but by now there are a few working on behalf of Democratic candidates as well.
Ironically, most of the members of Congress that these groups target are those in the middle. By now there are very few northeastern Republicans left (none at all from New England states in the House of Representatives) and only a couple of southern Democrats who come from districts that are not majority African-American. In particular, the northeastern Republicans have been replaced by Democrats who are almost all very liberal (so among the least likely Democrats to vote against the party line) and the southern Democrats have been replaced by very conservative Republicans who are similarly likely to march in lockstep. Since it was northeastern Republicans and Southern Democrats who traditionally were those most likely to vote for compromise or provide the key votes in moving legislation forward that might be of a bipartisan nature, what this means is that Congress is very polarized. To exacerbate this, most of the money is spent in 'swing districts' that are more likely to elect moderates to Congress. To cite one example, the district I live in changed partisan hands in 2008, 2010 and 2012. That makes it among the swingiest district in the country, and not surprisingly we see a great deal of political ad spending (almost all negative.) Members elected in a district like this, who might not be all that ideological otherwise, are pushed to toe their own party line because the attack ads will come regardless so in accordance with the old saying that 'if you will call me the devil whether I am or not, then I might as well be the devil' often they find the best path to re-election is to fire up their base (since the other side will turn out against them anyway) so therefore they are more likely to swing to that side.
In the short term this favors Republicans, if only because Republicans controlled redistricting so well after the 2010 election that they were able to draw a map that elected a Republican majority in 2012 even though Democrats got more votes FOR CONGRESS in 2012. In 2020, it will be a Presidential election year though so it is unlikely that Republicans will be able to maintain the kind of control over legislatures that they had after 2010, so their control of the House, if unlikely to be broken before then, may well be broken after 2020. In the long term however, the change is likely to simply harm communities across most of America. That is because the people who donate to the large Super-PACs are mainly national donors (even if we don't know all of what who donated, we do know that they are people with a national, rather than a local, agenda.) Since pork is also now banned, there is virtually nothing that a member of Congress can do that will win more votes in their district than making sure they are in the good graces of the Super-PACs who are running ads in their districts. As they will be attacked by the other side's PAC's, their main goal will be to give their own financial backers what they are asking for. In such a scenario, individual voters are less and less important, and that is the real tragedy of what we have come to.