Both parties are just different flavors of big government with different priorities for their big government control/spending.
The parties are coalitions of smaller political groupings that agree on some issues, and disagree on others. They unite in coalitions because that's the only way to win in a first past the post system like we have.
There used to be some core issues on which there was near universal agreement -- protection of free political speech, control over the borders, respect for elections, etc.. Because clear majorities agreed on those things, we argued about other things like the size/scope of government.
But those issues have now moved from being essentially non-political to being core issues of dispute for which we have to fight. Because the political battleground has broadened beyond the debate over the role of government, and now involves fighting over even more fundamental questions, the coalition has changed.
I'm a small government conservative who would love to get back to that fight. But the fight that the left has now started over those broader issues must be given priority, or everything else is moot.