Its that during different periods in the past the two sides have had different positions on the issues. For example, in 1960 left wing politicians such as Rockefeller (R) and JFK (D) favored greater defense spending while more right-wing pols such as Nixon (R) did not. One can cite many more examples.
Here’s the core of the problem.
As American civilization has grown, American government has not grown at the same pace. The gaps between the size of government and the need for government has caused the problem. During the 19th. Century government was smaller than was needed while in recent decades the government has been larger than needed.
When did the government tax too much, regulate too much, and spend too much? - And when did it do those things too little? Different times, different answers.