The only problem with your analysis is that the GOP has done quite a bit of its own new costly and irreversible entitlement programs.
And it will continue to do so. Nixon came up with the new Hispanic protected minority category that entrenched racial preferences for millions of people. Reagan came up with the amnesty program that legalized millions of Democrats, and is responsible for turning California deep blue (and Texas a little further down the road) and other states near Mexico a distinct purple*. Bush I raised taxes so Clinton could take credit for reducing them. Bush II came up with No Child Left Behind and Medicare Part D. And yet any of these Republicans would have been superior to any of the Democratic alternatives.
* I'd argue Reagan was probably the worst of them all, in terms of destroying GOP majorities - his importation of tens of millions of illegals created irreversible (and adverse to the GOP) demographic facts on the ground. We are very fortunate that the GOP grassroots were able to prevent Bush II from enacting his immigration reform, but I think it's undeniable that either Gore or Kerry would have been worse than Bush II.