Yes the GOP has its ups and downs and on occasion veers left of center on this or that going all the way to at least Nixon who saddled us with the EPA. Reagan was condemned as Trump has been for excessive spending but with the exception of COVID which was something NO President in U.S. history has had to deal with in the same way, both spent for the benefit of a strong, free, prosperous, secure America.
Bush 43 in many areas--defense, education, energy, legal and illegal immigration, environment--would have made any old guard Democrat proud as he straddled and often shifted left of the line between left and right.
The actual spending record of each administration is illustrated here:
https://www.cato.org/blog/century-federal-spending-1925-2025 and when compared to GDP Trump's record wasn't all that bad.
The only real difference between the two parties are the constituents they represent and depend on for votes. Those who reject many liberties and want to be governed, i.e. cared for from cradle to grave, most often vote Democrat.
Those who want their unalienable rights secured including liberty of thought, speech, choice, options, opportunity, innovation, entrepreneurship and ability to achieve visions for a strong, free, prosperous, secure America most often vote Republican.
Each party will throw their constituents the kinds of bones they most value.