At some point you have to realize it is not stupidity, but rather calculation. They are happy to be the permanent minority as long as the benefits of being a member of the club continue to increase. If they win, they might be forced to deliver on promises of taking power away from the government. That is something your average GOPer doesn’t want.
I had a conversation about this with my brother a while back. His comment was that all through the 1970s and 1980s, he thought "If only the Republicans had a majority in Congress, things would be different." For much of our lives, we never thought it possible. It seemed the democrats morphed into communists and their grip on the House of Representatives was perpetual. But then, the Republicans took the House in 1994...
and for a while it appeared there would be change. But by 2002, it was clear that nothing had.
So I have sadly come to the same conclusion that you have. The concept of limited government, individual liberty, and private enterprise are all empty slogans used to collect votes when expedient. There is no real desire to change DC, and being in the minority gives the GOP cover for why they don't.